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Objective: to describe the marked variability in clinical and biochemical patterns that are associated with a p.R209H GH1 missense variant in a large Argentinean pedigree, which makes the diagnosis of GHD elusive. Design: We describe a non-consanguineous pedigree composed by several individuals with short stature, including 2 pediatric patients with typical diagnosis of isolated growth hormone deficiency (IGHD) and 4 other siblings with severe short stature, low serum IGF-1 and IGFBP-3, but normal stimulated GH levels, suggesting growth hormone insensitivity (GHI) in the latter group. Results: Patients with classical IGHD phenotype carried a heterozygous variant in GH1: c.626G>A (p.R209H). Data from the extended pedigree suggested GH1 as the initial candidate gene, which showed the same pathogenic heterozygous GH1 variant in the four siblings with short stature and a biochemical pattern of GHI. Conclusions: We suggest considering GH1 sequencing in children with short stature associated to low IGF-1 and IGFBP-3 serum levels, even in the context of normal response to growth hormone provocative testing (GHPT). Fil: Sanguineti, Nora María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Braslavsky, Debora Giselle. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Scaglia, Paula Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Keselman, Ana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Ballerini, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Ropelato, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Suco, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Vishnopolska, Sebastián Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina Fil: Berenstein, Ariel José. Gobierno de la Ciudad de Buenos Aires. Instituto Multidisciplinario de Investigaciones en Patologías Pediátricas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto Multidisciplinario de Investigaciones en Patologías Pediátricas; Argentina Fil: Jasper, Hector Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Domene, Horacio Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Rey, Rodolfo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina Fil: Pérez Millán, Maria I.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; Argentina Fil: Camper, Sally. University Of Michigan. College Of Literature, Sciences And Arts. Molecular, Cellular And Developmental Biology; Estados Unidos Fil: Bergadá, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Gobierno de la Ciudad de Buenos Aires. Centro de Investigaciones Endocrinológicas "Dr. César Bergada". Fundación de Endocrinología Infantil. Centro de Investigaciones Endocrinológicas "Dr. César Bergada"; Argentina

Germline mutations in BRAF and other components of the MAPK pathway are associated with the congenital syndromes collectively known as RASopathies. Here, we report the association of Septo-Optic Dysplasia (SOD) including hypopituitarism and Cardio-Facio-Cutaneous (CFC) syndrome in patients harbouring mutations in BRAF. Phosphoproteomic analyses demonstrate that these genetic variants are gain-of-function mutations leading to activation of the MAPK pathway. Activation of the MAPK pathway by conditional expression of the BrafV600E/+ allele, or the knock-in BrafQ241R/+ allele (corresponding to the most frequent human CFC-causing mutation, BRAF p.Q257R), leads to abnormal cell lineage determination and terminal differentiation of hormone-producing cells, causing hypopituitarism. Expression of the BrafV600E/+ allele in embryonic pituitary progenitors leads to an increased expression of cell cycle inhibitors, cell growth arrest and apoptosis, but not tumour formation. Our findings show a critical role of BRAF in hypothalamo-pituitary-axis development both in mouse and human and implicate mutations found in RASopathies as a cause of endocrine deficiencies in humans., Mutations in components of the MAP kinase pathway are associated with a group of syndromes known as RASopathies. Here, the authors identify gain-of-function mutations in BRAF in patients with RASopathies and congenital hypopituitarisms. This article demonstrates a central role for BRAF in the development of the hypothalamo-pituitary axis leading to endocrine deficiencies in patients with RASopathies.

Recent studies have shown a novel mechanism of combined pituitary hormone deficiency associated with mutations in POU1F1, altering the balance of alternative-splicing, which results in over-expression of the beta isoform of POU1F1. These studies underscore the need for biologists, in the context of routine molecular diagnosis of this condition, to investigate alternative splicing in POU1F1 as well as in other genes.

Maternal and fetal sources of thyroid hormone are important for the development of many organ systems. Thyroid hormone deficiency causes variable intellectual disability and hearing impairment in mouse and man, but the basis for this variation is not clear. To explore this variation, we studied two thyroid hormone-deficient mouse mutants with mutations in pituitary-specific transcription factors, POU1F1 and PROP1, that render them unable to produce thyroid stimulating hormone. DW/J-Pou1f1dw/dw mice have profound deafness and both neurosensory and conductive hearing impairment, while DF/B-Prop1df/df mice have modest elevations in hearing thresholds consistent with developmental delay, eventually achieving normal hearing ability. The thyroid glands of Pou1f1 mutants are more severely affected than those of Prop1df/df mice, and they produce less thyroglobulin during the neonatal period critical for establishing hearing. We previously crossed DW/J-Pou1f1dw/+ and Cast/Ei mice and mapped a major locus on Chromosome 2 that protects against hypothyroidism-induced hearing impairment in Pou1f1dw/dw mice: modifier of dw hearing (Mdwh). Here we refine the location of Mdwh by genotyping 196 animals with 876 informative SNPs, and we conduct novel mapping with a DW/J-Pou1f1dw/+ and 129/P2 cross that reveals 129/P2 mice also have a protective Mdwh locus. Using DNA sequencing of DW/J and DF/B strains, we determined that the genes important for thyroid gland function within Mdwh vary in amino acid sequence between strains that are susceptible or resistant to hypothyroidism-induced hearing impairment. These results suggest that the variable effects of congenital hypothyroidism on the development of hearing ability are attributable to genetic variation in postnatal thyroid gland folliculogenesis and function.

Targeted oncogenesis is the process of driving tumor formation by engineering transgenic mice that express an oncogene under the control of a cell-type specific promoter. Such tumors can be adapted to cell culture, providing immortalized cell lines. To make it feasible to follow the process of tumorigenesis and increase the opportunity for generating cell lines, we developed a mouse strain that expresses SV40 T antigens in response to Cre-recombinase. Using CRISPR/Cas9 we inserted a cassette with coding sequences for SV40 T antigens and an internal ribosome entry site with green fluorescent protein cassette (IRES-GFP) into the Rosa26 locus, downstream from a stop sequence flanked by loxP sites: Rosa26LSL-SV40-GFP. These mice were mated with previously established Prop1-cre and Tshb-cre transgenic lines. Both the Rosa26LSL-SV40-GFP/+; Prop1-cre and Rosa26LSL-SV40-GFP/+; Tshb-cre mice developed fully penetrant dwarfism and large tumors by 4 weeks. Tumors from both of these mouse lines were adapted to growth in cell culture. We have established a progenitor-like cell line (PIT-P1) that expresses Sox2 and Pitx1, and a thyrotrope-like cell line (PIT-T1) that expresses Pou1f1 and Cga. These studies demonstrate the utility of the novel, Rosa26 LSL-SV40-GFP mouse line for reliable targeted oncogenesis and development of unique cell lines.

Objective The transcription factor OTX2is implicated in ocular, craniofacial, and pituitary development. Design We aimed to establish the contribution of OTX2 mutations in congenital hypopituitarism patients with/without eye abnormalities, study functional consequences, and establish OTX2 expression in the human brain, with a view to investigate the mechanism of action. Methods We screened patients from the UK (n = 103), international centres (n = 24), and Brazil (n = 282); 145 were within the septo-optic dysplasia spectrum, and 264 had no eye phenotype. Transactivation ability of OTX2 variants was analysed in murine hypothalamic GT1-7 neurons. In situ hybridization was performed on human embryonic brain sections. Genetically engineered mice were generated with a series of C-terminal OTX2 variants. Results Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities; an affected relative of one patient harboured the same mutation without an ocular phenotype. OTX2 truncations led to significant transactivation reduction. A missense variant was identified in another patient without eye abnormalities; however, studies revealed it was most likely not causative. In the mouse, truncations proximal to aa219 caused anophthalmia, while distal truncations and the missense variant were tolerated. During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary. Conclusions OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree. Our data suggest that the endocrine phenotypes in patients with OTX2 mutations are of hypothalamic origin.

Purpose Congenital hypopituitarism (CH) can present in isolation or with other birth defects. Mutations in multiple genes can cause CH, and the use of a genetic screening panel could establish the prevalence of mutations in known and candidate genes for this disorder. It could also increase the proportion of patients that receive a genetic diagnosis. Methods We conducted target panel genetic screening using single-molecule molecular inversion probes sequencing to assess the frequency of mutations in known hypopituitarism genes and new candidates in Argentina. We captured genomic deoxyribonucleic acid from 170 pediatric patients with CH, either alone or with other abnormalities. We performed promoter activation assays to test the functional effects of patient variants in LHX3 and LHX4. Results We found variants classified as pathogenic, likely pathogenic, or with uncertain significance in 15.3% of cases. These variants were identified in known CH causative genes (LHX3, LHX4, GLI2, OTX2, HESX1), in less frequently reported genes (FOXA2, BMP4, FGFR1, PROKR2, PNPLA6) and in new candidate genes (BMP2, HMGA2, HNF1A, NKX2-1). Conclusion In this work, we report the prevalence of mutations in known CH genes in Argentina and provide evidence for new candidate genes. We show that CH is a genetically heterogeneous disease with high phenotypic variation and incomplete penetrance, and our results support the need for further gene discovery for CH. Identifying population-specific pathogenic variants will improve the capacity of genetic data to predict eventual clinical outcomes.

The transcription factor ISL1 is expressed in pituitary gland stem cells and the thyrotrope and gonadotrope lineages. Pituitary-specific Isl1 deletion causes hypopituitarism with increased stem cell apoptosis, reduced differentiation of thyrotropes and gonadotropes, and reduced body size. Conditional Isl1 deletion causes development of multiple Rathke’s cleft-like cysts, with 100% penetrance. Foxa1 and Foxj1 are abnormally expressed in the pituitary gland and associated with a ciliogenic gene-expression program in the cysts. We confirmed expression of FOXA1, FOXJ1, and stem cell markers in human Rathke’s cleft cyst tissue, but not craniopharyngiomas, which suggests these transcription factors are useful, pathological markers for diagnosis of Rathke’s cleft cysts. These studies support a model whereby expression of ISL1 in pituitary progenitors drives differentiation into thyrotropes and gonadotropes and without it, activation of FOXA1 and FOXJ1 permits development of an oral epithelial cell fate with mucinous cysts. This pituitary-specific Isl1 mouse knockout sheds light on the etiology of Rathke’s cleft cysts and the role of ISL1 in normal pituitary development. Fil: Brinkmeier, Michelle L.. University of Michigan; Estados Unidos Fil: Bando, Hironori. University of Michigan; Estados Unidos Fil: Camarano, Adriana Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Fujio, Shingo. Kagoshima University; Japón Fil: Yoshimoto, Koji. Kagoshima University; Japón Fil: Silva Junqueira de Souza, Flávio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Camper, Sally. University of Michigan; Estados Unidos

The Pit-1/GHF-1 (Pit-1) transcription factor is important for the development of anterior pituitary cells that produce GH and PRL. We examined the expression of Pit-1 mRNA in pituitary tissues from rats and mice. Analysis of pituitaries from normal and GHRH transgenic mice showed that Pit-1 transcripts were readily detected in normal, hyperplastic, and neoplastic pituitaries. A cell line (GHRH-CL1) established from a GhRH transgenic mouse pituitary tumor in our laboratory also expressed Pit-1 mRNA. Normal rat pituitaries and those with estrogen-induced PRL cell hyperplasia expressed Pit-1 mRNA. There was a decrease in Pit-1 mRNA in hyperplastic rat pituitaries concomitant with a decrease In GH mRNA amounts and an increase in PRL mRNA amounts after estrogen treatment. Similarly, analysis of GH3 cells in vitro showed that estrogen and bFGF modulated PRL but not Pit-1 mRNA levels. Pit-1 mRNA was localized by combined in situ hybridization and immunohistochemistry to predominantly GH and PRL cells, although some TSH and LH cells in the rat pituitary also expressed Pit-1 mRNA, indicating wide distribution of the mRNA for this transcription factor in various anterior pituitary cell types. Analysis of cell proliferation in normal rat pituitary and GH3 cells revealed that estrogen and bFGF stimulated cell proliferation in normal pituitaries but inhibited proliferation in GH3 cells, whereas Pit-1 transcripts remained unchanged in both groups of cultured cells. These results indicate that Pit-1 mRNA is readily detected in normal, hyperplastic, and neoplastic rodent pituitaries. Changes in Pit-1 mRNA amounts appear to correlate more closely with changes in GH than PRL mRNA levels in cultured pituitary cells.Endocr Pathol 4:146–154, 1993.

Combined pituitary hormone deficiency (CPHD) is an important clinical problem caused by mutations in more than 30 different genes. Six genes in the Sonic Hedgehog (SHH) signalling pathway are reported to cause CPHD. SHH signaling is essential to induce pituitary cell identity in cells of Rathke’s pouch by stimulating expression of the transcription factors Lhx3 and Lhx4. In the absence of SHH signaling, a repressive isoform of the transcription factor GLI2 (Gli-Kruppel family member 2) suppresses gene expression. In the presence of SHH signaling, the activating form of GLI2 gains access to the nucleus and induces expression of downstream target genes. Heterozygous GLI2 loss of function mutations are found in patients with holoprosencephaly (HPE), HPE-like phenotypes associated with pituitary anomalies, and combined pituitary hormone deficiency with or without other extra-pituitary findings. We sought to identify the cause of CPHD in 171 unrelated patients diagnosed with or without extra-pituitary manifestations that were recruited from several Argentinean medical centers. We conducted panel sequencing, and identified GLI2 heterozygous variants that were rare and predicted to be deleterious in two unrelated patients, (p.L761P and p.1404Lfs) and a single, heterozygous, rare, likely deleterious GLI2 variant identified by exome sequencing (p.A203T). p.L761P and p.A203T variants were previously reported as candidates for HPE/CPHD, no functional studies were carried out to determine the effect of the variants on the gene function. We performed functional analysis of these variants using a mammalian cell line (NIH/3T3-CG) previously engineered to be a sensor for SHH signaling. It was stably transfected with a reporter gene that expresses GFP in response to GLI2 activation by a SHH agonist. We modified this cell line to assay GLI2 variants. We created a homozygous knock out of both endogenous Gli2 genes using CRISPR-Cas9 editing, and individual cell clones were selected for loss of GFP expression in response to SHH agonist treatment by FACS. We verified that transfecting the knockout cells with wild type Gli2 restored SHH responsive GFP expression. We assayed the ability of three patient GLI2 variants to rescue GFP expression and SHH agonist responsiveness and found that all three failed to fully rescue to wild type levels. This supports the hypothesis that the GLI2 variants in three CPHD patients are likely pathogenic. Thus, we identified three likely pathogenic GLI2 mutations in CPHD patients from Argentina. The variable phenotype of patients with GLI2 mutations worldwide could be caused by variation in other genes, environmental exposures, maternal effects, and/or epigenetic factors.

The transcription factor OTX2 is implicated in pituitary, ocular and craniofacial development. Mutations have been described in patients with variable congenital hypopituitarism (CH) ranging from isolated growth hormone deficiency (IGHD) to combined pituitary hormone deficiency (CPHD) with/without an ectopic posterior pituitary (EPP).We aimed (i) to establish the contribution of OTX2 mutations in the etiology of CH in a sub-cohort of patients and to study their functional consequences and (ii) establish a detailed human OTX2 expression profile in a hypothalamo-pituitary (HP) context. We screened 127 patients from national (n=103) and international centers (n=24) on the septo-optic dysplasia (SOD) spectrum with variable eye abnormalities. Eye abnormalities included micro/anophthalmia, retinal dystrophy and/or coloboma in 29 of these patients, with the rest having optic nerve hypoplasia (ONH). An EPP was reported on MRI in 35 patients. The cohort previously tested negative for mutations in HESX1, SOX2, SOX3, PROKR2 and GH1. Transactivation assays involved a dual-luciferase reporter in murine hypothalamic GT1-7 neurons transiently transfected with OTX2 constructs. In situ hybridization was performed to analyze human brain OTX2 expression during embryogenesis. Seven heterozygous OTX2 changes were identified: two chromosomal deletions spanning OTX2 in patients with micro/anophthalmia, GHD and an EPP, with one patient having cerebellar hypoplasia. Three missense substitutions resulting in truncated proteins: (i) the previously reported p.S138* and (ii) p.C170*, in two patients with retinal dystrophy, EPP and IGHD respectively, and (iii) the novel p.E79* in a patient with micro/anophthalmia, EPP and CPHD. A novel insertion-deletion resulting in a truncated protein p.S167* in a patient with microphthalmia, GHD, ONH, EPP and an enlarged abnormal pituitary, and a novel deletion resulting in a frameshift p.Val139Aspfs*39 in a patient with microcephaly, microphthalmia, ONH and an EPP were also identified. The human OTX2 variants caused a significant reduction in transactivation compared to wild type. Our gene expression data identified human OTX2 transcripts in the posterior pituitary, retina, ear, thalamus, choroid plexus, and in the hypothalamus during embryogenesis, but not in RP. To conclude, we identified OTX2 variants in 7 unrelated CH patients with eye abnormalities including 3 with retinal dystrophy and one with a cerebellar abnormality. As OTX2 is involved at multiple levels during HP development, these patients should be monitored for evolving endocrinopathies. Human OTX2 is expressed in the posterior pituitary, the retina and the ear at CS19 and 20 (between 6-7 weeks gestation), and in areas of the hindbrain at CS23, but not in RP at any stage analyzed in this study. The endocrine phenotypes in patients with OTX2 mutations are most likely of hypothalamic origin.

Introduction: Hypopituitarism is defined as a deficiency of one or more pituitary hormones. Pathogenic allelic variants in genes implicated in pituitary development were associated in 15% of the patients with congenital hypopituitarism (CH). To improve the molecular diagnosis we performed whole exome sequencing of ten patients born from consanguineous parents with CH. One patient with GH, TSH, ACTH and LH/FSH deficiencies presented an allelic variant c.865G>A, p.V289I in CDH2 gene (exon 7) in homozygous state that was absent in populational databanks. CDH2 produces an N-cadherin protein implicated in cellular adhesion and is responsible for epithelial-mesenchymal transition during pituitary development and differentiation. Aim: To analyze the CDH2 gene in a cohort of unrelated patients with CH. Methods: We selected 143 patients with CH from a single Brazilian center. Genomic DNA, extracted by salting out technique, was submitted to PCR amplification of 15 coding regions, except CG rich exon 1, of the CDH2 gene followed by the Sanger sequencing. Rare allelic variant frequency (MAFA, p.V289I) was found in heterozygous state in a male patient with short stature diagnosed with GH and TSH deficiencies at the age of 11 that evolved with LH/FSH and ACTH deficiencies. Family segregation showed 3 among 11 normal siblings heterozygous carriers. This variant is rare, in heterozygous state, in populational data bank and it was predicted as deleterious or possibly harmful. The allelic variant c.1202C> A (p.A401D), in exon 9, was found in heterozygous state in a female patient with isolated GH deficiency and intellectual disability. The variant was absent in the databases and predicted as deleterious or disease-causing. The variant was absent in the mother and stepsister and the father was not available for testing. The c.1430_1431delCCinsTG allelic variant (p.P477L) was found in heterozygous state in a patient with septo-optic dysplasia, GH, TSH and ACTH deficiencies. It was absent in the databases and was predicted as deleterious or disease causing. The Human Splicing Finder predicted exonic splicing enhancer breakdown leading to the loss of 93 nucleotides. Normal mother is heterozygous carrier suggesting incomplete penetrance. Conclusion: Heterozygous variants in CDH2 were found in 2% of a cohort of Brazilian patients with congenital hypopituitarism and none in homozygous or compound heterozygous state. Further CDH2 analyses in unrelated patients from different ethnic backgrounds are needed to establish the role CDH2 variants in the etiology of congenital hypopituitarism.

Advances in genomic technologies are revolutionizing the practice of medicine by delivering molecular diagnoses that can be informative for prognosis and treatment of genetic disorders. Most of the known genetic causes of multiple pituitary hormone deficiency have been investigated as monogenic disorders. It can be challenging to predict clinical features from genetic data, as loss of function mutations in some genes can present with a spectrum of phenotypes ranging from craniofacial abnormalities, intellectual disability, and neurosensory and neuroendocrine defects to pituitary hormone deficiency with no other abnormalities. Although maternal exposures could be contributing factors, the contribution of rare, deleterious variation in other genes is a likely contributor. In humans, loss of function mutations in the transcription factor SIX3 cause variable, autosomal dominant holoprosencephaly with incomplete penetrance, and mouse models recapitulate some of the clinical features. Because Six3 and Pou1f1 gene expression patterns overlap in pituitary development, we hypothesized that doubly heterozygous mice (Six3+/-; Pou1f1+/dw) might have pituitary anomalies not present in singly heterozygous mice. We intercrossed Six3+/- and Pou1f1+/dw mice to produce doubly heterozygous animals. At e11.5, both Six3+/- and Six3+/-; Pou1f1+/dw exhibited abnormal morphology of the developing infundibulum and Rathke’s pouch, although ventral diencephalon expression of Tle4, Fgf10, and Nkx2.1 appeared normal. Both newborn Six3+/- and Six3+/-; Pou1f1+/dw littermates had abnormal pituitary gland morphology that resembled that of Aes-/-. AES is a co-repressor that interacts with SIX3. Specification of vasopressin neurons and anterior lobe hormone cell types appeared normal. Mice of all genotypes were born in expected Mendelian ratios (N=144, p=0.49), and there were no significant differences in body weight at 3 wks. A portion of the Six3+/- and doubly heterozygous mice developed hydrocephalus, exhibited failure to thrive, and died (6-9% of N=82, 85, respectively). At 6 wks, 25% (N=61) of the Six3+/-; Pou1f1+/dw animals exhibited striking pituitary dysmorphology in which the rostral aspect of the pituitary penetrated the palate. This was not observed in single heterozygotes. These results reveal that haploinsufficiency for Six3 affects Rathke’s pouch formation, resulting in pituitary gland dysmorphology in and around the stem cell niche. A significant portion of the Six3+/-; Pou1f1+/dw doubly heterozygous mice have a more pronounced pituitary phenotype than Six3+/-, supporting the possibility of digenic pituitary disease and highlighting phenotypic variability. Genetically engineered mice provide an excellent tool for assessing the possibility of gene-gene interactions that could enhance the severity of hypopituitarism and associated craniofacial development.

Transcription factors and signaling pathways that regulate stem cells and specialized hormone-producing cells in the pituitary gland have been the subject of intense study and have yielded a mechanistic understanding of pituitary organogenesis and disease. However, the regulation of stem cell proliferation and differentiation, the heterogeneity among specialized hormone-producing cells, and the role of nonendocrine cells in the gland remain important, unanswered questions. Recent advances in single-cell RNA sequencing (scRNAseq) technologies provide new avenues to address these questions. We performed scRNAseq on ∼13,663 cells pooled from six whole pituitary glands of 7-week-old C57BL/6 male mice. We identified pituitary endocrine and stem cells in silico, as well as other support cell types such as endothelia, connective tissue, and red and white blood cells. Differential gene expression analyses identify known and novel markers of pituitary endocrine and stem cell populations. We demonstrate the value of scRNAseq by in vivo validation of a novel gonadotrope-enriched marker, Foxp2. We present novel scRNAseq data of in vivo pituitary tissue, including data from agnostic clustering algorithms that suggest the presence of a somatotrope subpopulation enriched in sterol/cholesterol synthesis genes. Additionally, we show that incomplete transcriptome annotation can cause false negatives on some scRNAseq platforms that only generate 3′ transcript end sequences, and we use in vivo data to recover reads of the pituitary transcription factor Prop1. Ultimately, scRNAseq technologies represent a significant opportunity to address long-standing questions regarding the development and function of the different populations of the pituitary gland throughout life.

Dietary vitamin A is metabolized into bioactive retinoic acid (RA) in vivo and regulates the development of many embryonic tissues. RA signaling is active in the oral ectoderm-derived tissues of the neuroendocrine system, but its role there has not yet been fully explored. We show here that RA signaling is active during pituitary organogenesis and dependent on the pituitary transcription factor Prop1. Prop1-mutant mice show reduced expression of the aldehyde dehydrogenase gene Aldh1a2, which metabolizes the vitamin A–intermediate retinaldehyde into RA. To elucidate the specific function of RA signaling during neuroendocrine development, we studied a conditional deletion of Aldh1a2 and a dominant-negative mouse model of inhibited RA signaling during pituitary organogenesis. These models partially phenocopy Prop1-mutant mice by exhibiting embryonic pituitary dysmorphology and reduced hormone expression, especially thyrotropin. These findings establish the role of RA in embryonic pituitary stem cell progression to differentiated hormone cells and raise the question of gene-by-environment interactions as contributors to pituitary development and disease.

The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over 30 causal genes have been identified. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified two children with neonatal GH and TSH deficiency and stalk interruption who were doubly heterozygous for rare, likely deleterious variants in SIX3 and POU1F1. Functional studies demonstrated that both variants are disruptive. We used Six3 and Pou1f1 loss of function mice to assess the genetic interaction between Six3 and Pou1f1. Six3 heterozygotes have variable pituitary gland dysmorphology, while Pou1f1 heterozygotes are normal. A significant portion of the Six3+/-; Pou1f1+/dw doubly heterozygous mice have a more pronounced pituitary phenotype than Six3+/-, supporting the possibility of digenic pituitary disease. To understand the role of SIX3 in pituitary and hypothalamic development, we used Prop1-cre and Nkx2.1-cre to delete Six3. Disruption of Six3 expression in Rathke’s pouch caused poor activation of Lhx3 expression and arrested anterior pituitary development. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination and failed to induce FGF and BMP signaling, which normally drive expansion of Rathke’s pouch. By E11.5 cells in Rathke’s pouch underwent apoptosis. The Nkx2.1-cre, Six3flox/flox embryos failed to activate expression of Lhx2 and Tbx3 in the neural ectoderm. These embryos had elevated CCND1, MYCN, and Axin2 expression in the area of the presumptive infundibulum. This indicates that SIX3 is necessary to repress cell proliferation and Wnt/beta-catenin signals to promote formation of the pituitary stalk. Thus, Six3 has essential roles in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities or PSIS.

The hypothalamic-pituitary axes are the coordinating centers for multiple endocrine gland functions and physiological processes. Defects in the hypothalamus or pituitary gland can cause reduced growth and severe short stature, affecting approximately 1 in 4000 children, and a large percentage of cases of pituitary hormone deficiencies do not have an identified genetic cause. SOX21 is a protein that regulates hair, neural, and trophoblast stem cell differentiation. Mice lacking Sox21 have reduced growth, but the etiology of this growth defect has not been described. We studied the expression of Sox21 in hypothalamic-pituitary development and examined multiple endocrine axes in these mice. We find no evidence of reduced intrauterine growth, food intake, or physical activity, but there is evidence for increased energy expenditure in mutants. In addition, despite changes in pituitary hormone expression, hypothalamic-pituitary axes appear to be functional. Therefore, SOX21 variants may be a cause of non-endocrine short stature in humans.

Thyrotrope hyperplasia and hypertrophy are common responses to primary hypothyroidism. To understand the genetic regulation of these processes, we studied gene expression changes in the pituitaries of Cga−/− mice, which are deficient in the common α-subunit of TSH, LH, and FSH. These mice have thyrotrope hypertrophy and hyperplasia and develop thyrotrope adenoma. We report that cell proliferation is increased, but the expression of most stem cell markers is unchanged. The α-subunit is required for secretion of the glycoprotein hormone β-subunits, and mutants exhibit elevated expression of many genes involved in the unfolded protein response, consistent with dilation and stress of the endoplasmic reticulum. Mutants have elevated expression of transcription factors that are important in thyrotrope function, such as Gata2 and Islet 1, and those that stimulate proliferation, including Nupr1, E2f1, and Etv5. We characterized the expression and function of a novel, overexpressed gene, transcription elongation factor A (SII)-like 5 (Tceal5). Stable expression of Tceal5 in a pituitary progenitor cell line is sufficient to increase cell proliferation. Thus, Tceal5 may act as a proto-oncogene. This study provides a rich resource for comparing pituitary transcriptomes and an analysis of gene expression networks.

Mutations in PROP1, the most common known cause of combined pituitary hormone deficiency in humans, can result in the progressive loss of all hormones of the pituitary anterior lobe. In mice, Prop1 mutations result in the failure to initiate transcription of Pou1f1 (also known as Pit1) and lack somatotropins, lactotropins, and thyrotropins. The basis for this species difference is unknown. We hypothesized that Prop1 is expressed in a progenitor cell that can develop into all anterior lobe cell types, and not just the somatotropes, thyrotropes, and lactotropes, which are collectively known as the PIT1 lineage. To test this idea, we produced a transgenic Prop1-cre mouse line and conducted lineage-tracing experiments of Prop1-expressing cells. The results reveal that all hormone-secreting cell types of both the anterior and intermediate lobes are descended from Prop1-expressing progenitors. The Prop1-cre mice also provide a valuable genetic reagent with a unique spatial and temporal expression for generating tissue-specific gene rearrangements early in pituitary gland development. We also determined that the minimal essential sequences for reliable Prop1 expression lie within 10 kilobases of the mouse gene and demonstrated that human PROP1 can substitute functionally for mouse Prop1. These studies enhance our understanding of the pathophysiology of disease in patients with PROP1 mutations. Fil: Davis, Shannon W.. University of South Carolina; Estados Unidos Fil: Keisler, Jessica L.. University of South Carolina; Estados Unidos Fil: Pérez Millán, María Inés. University of Michigan; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Schade, Vanessa. University of Michigan; Estados Unidos Fil: Camper, Sally A.. University of Michigan; Estados Unidos

Pituitary gonadotropins follicle-stimulating hormone and luteinizing hormone are heterodimeric glycoproteins expressed in gonadotropes. They act on gonads and promote their development and functions including steroidogenesis and gametogenesis. Although transcriptional regulation of gonadotropin subunits has been well studied, the post-transcriptional regulation of gonadotropin subunits is not well understood. To test if microRNAs regulate the hormone-specific gonadotropin β subunits in vivo, we deleted Dicer in gonadotropes by a Cre-lox genetic approach. We found that many of the DICER-dependent microRNAs, predicted in silico to bind gonadotropin β subunit mRNAs, were suppressed in purified gonadotropes of mutant mice. Loss of DICER-dependent microRNAs in gonadotropes resulted in profound suppression of gonadotropin-β subunit proteins and, consequently, the heterodimeric hormone secretion. In addition to suppression of basal levels, interestingly, the post-gonadectomy-induced rise in pituitary gonadotropin synthesis and secretion were both abolished in mutants, indicating a defective gonadal negative feedback control. Furthermore, mutants lacking Dicer in gonadotropes displayed severely reduced fertility and were rescued with exogenous hormones confirming that the fertility defects were secondary to suppressed gonadotropins. Our studies reveal that DICER-dependent microRNAs are essential for gonadotropin homeostasis and fertility in mice. Our studies also implicate microRNAs in gonadal feedback control of gonadotropin synthesis and secretion. Thus, DICER-dependent microRNAs confer a new layer of transcriptional and post-transcriptional regulation in gonadotropes to orchestrate the hypothalamus-pituitary-gonadal axis physiology.

SUMMARY Isolated growth hormone deficiency (IGHD) is the most common pituitary hormone deficiency and, clinically, patients have delayed bone age. High sequence similarity between CYP21A2 gene and CYP21A1P pseudogene poses difficulties for exome sequencing interpretation. A 7.5 year-old boy born to second-degree cousins presented with severe short stature (height SDS −3.7) and bone age of 6 years. Clonidine and combined pituitary stimulation tests revealed GH deficiency. Pituitary MRI was normal. The patient was successfully treated with rGH. Surprisingly, at 10.8 years, his bone age had advanced to 13 years, but physical exam, LH and testosterone levels remained prepubertal. An ACTH stimulation test disclosed a non-classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency explaining the bone age advancement and, therefore, treatment with cortisone acetate was added. The genetic diagnosis of a homozygous mutation in GHRHR (p.Leu144His), a homozygous CYP21A2 mutation (p.Val282Leu) and CYP21A1P pseudogene duplication was established by Sanger sequencing, MLPA and whole-exome sequencing. We report the unusual clinical presentation of a patient born to consanguineous parents with two recessive endocrine diseases: non-classic congenital adrenal hyperplasia modifying the classical GH deficiency phenotype. We used a method of paired read mapping aided by neighbouring mis-matches to overcome the challenges of exome-sequencing in the presence of a pseudogene.

The pituitary organizer is a domain within the ventral diencephalon that expresses Bmp4, Fgf8, and Fgf10, which induce the formation of the pituitary precursor, Rathke's pouch, from the oral ectoderm. The WNT signaling pathway regulates this pituitary organizer such that loss of Wnt5a leads to an expansion of the pituitary organizer and an enlargement of Rathke's pouch. WNT signaling is classified into canonical signaling, which is mediated by β-CATENIN, and noncanonical signaling, which operates independently of β-CATENIN. WNT5A is typically classified as a noncanonical WNT; however, other WNT family members are expressed in the ventral diencephalon and nuclear localized β-CATENIN is observed in the ventral diencephalon. Therefore, we sought to determine whether canonical WNT signaling is necessary for regulation of pituitary organizer function. Using a conditional loss-of-function approach, we deleted β-catenin within the mouse ventral diencephalon. Mutant embryos have a smaller Rathke's pouch, resulting from a reduced pituitary organizer, especially Fgf8. This result suggests that canonical WNT signaling promotes pituitary organizer function, instead of inhibiting it. To test this hypothesis, we stimulated canonical WNT signaling in the ventral diencephalon using an inducible gain-of-function allele of β-catenin and found that stimulating canonical WNT signaling expands the domain of Fgf8 and results in a dysmorphic Rathke's pouch. These results demonstrate that canonical WNT signaling in the ventral diencephalon is necessary for proper expression of pituitary organizer genes and suggests that a balance of both canonical and noncanonical WNT signaling is necessary to ensure proper formation of Rathke's pouch.

The anterior pituitary gland is comprised of specialized cell-types that produce and secrete polypeptide hormones in response to hypothalamic input and feedback from target organs. These specialized cells arise from stem cells that express SOX2 and the pituitary transcription factor PROP1, which is necessary to establish the stem cell pool and promote an epithelial to mesenchymal-like transition, releasing progenitors from the niche. The adult anterior pituitary responds to physiological challenge by mobilizing the SOX2-expressing progenitor pool and producing additional hormone-producing cells. Knowledge of the role of signaling pathways and extracellular matrix components in these processes may lead to improvements in the efficiency of differentiation of embryonic stem cells or induced pluripotent stem cells into hormone producing cells in vitro. Advances in our basic understanding of pituitary stem cell regulation and differentiation may lead to improved diagnosis and treatment for patients with hypopituitarism. Fil: Cheung, Leonard Y. M.. University of Michigan; Estados Unidos Fil: Davis, Shannon W.. University of South Carolina; Estados Unidos Fil: Brinkmeier, Michelle L.. University of Michigan; Estados Unidos Fil: Camper, Sally A.. University of Michigan; Estados Unidos Fil: Pérez Millán, María Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; Argentina

Cocaine-and Amphetamine Regulated Transcript (CART) peptide is expressed in the brain, endocrine and neuroendocrine systems and secreted into the serum. It is thought to play a role in regulation of hypothalamic pituitary functions. Here we report a spatial and temporal analysis of Cart expression in the pituitaries of adult and developing normal and mutant mice with hypopituitarism. We found that Prop1 is not necessary for initiation of Cart expression in the fetal pituitary at e14.5, but it is required indirectly for maintenance of Cart expression in the postnatal anterior pituitary gland. Pou1f1 deficiency has no effect on Cart expression before or after birth. There is no 1:1 correspondence between CART and any particular cell type. In neonates, CART is detected primarily in non-proliferating, POU1F1-positive cells. CART is also found in some cells that express TSH and GH suggesting a correspondence with committed progenitors of the POU1F1 lineage. In summary, we have characterized the normal temporal and cell specific expression of CART in mouse development and demonstrate that postnatal CART expression in the pituitary gland requires PROP1.

Summary: Altered progesterone responsiveness leads to female infertility and cancer, but underlying mechanisms remain unclear. Mice with uterine-specific ablation of GATA binding protein 2 (Gata2) are infertile, showing failures in embryo implantation, endometrial decidualization, and uninhibited estrogen signaling. Gata2 deficiency results in reduced progesterone receptor (PGR) expression and attenuated progesterone signaling, as evidenced by genome-wide expression profiling and chromatin immunoprecipitation. GATA2 not only occupies at and promotes expression of the Pgr gene but also regulates downstream progesterone responsive genes in conjunction with the PGR. Additionally, Gata2 knockout uteri exhibit abnormal luminal epithelia with ectopic TRP63 expressing squamous cells and a cancer-related molecular profile in a progesterone-independent manner. Lastly, we found a conserved GATA2-PGR regulatory network in both human and mice based on gene signature and path analyses using gene expression profiles of human endometrial tissues. In conclusion, uterine Gata2 regulates a key regulatory network of gene expression for progesterone signaling at the early pregnancy stage. : Rubel et al. find that in the uterus, Gata2 regulates the expression of progesterone receptor and its ability to modulate transcription of genes required for receptivity and support of embryo implantation. Gata2 is critical for the uterus to maintain epithelial integrity and prevent stratification in response to an estrogen challenge. Keywords: GATA2, progesterone, progesterone receptor, TRP63, uterus, endometrium, infertility, path analysis, structural equation modeling, pregnancy

SummaryIntroduction Mutations in the transcription factor HESX1 can cause isolated growth hormone deficiency (IGHD) or combined pituitary hormone deficiency (CPHD) with or without septo-optic dysplasia (SOD). So far there is no clear genotype–phenotype correlation. Patients and Results We report four different recessive loss-of-function mutations in three unrelated families with CPHD and no midline defects or SOD. A homozygous p.R160C mutation was found by Sanger sequencing in two siblings from a consanguineous family. These patients presented with ACTH, TSH and GH deficiencies, severe anterior pituitary hypoplasia (APH) or pituitary aplasia (PA) and normal posterior pituitary. The p.R160C mutation was previously reported in a case with SOD, CPHD and ectopic posterior pituitary (EPP). Using exome sequencing, a homozygous p.I26T mutation was found in a Brazilian patient born to consanguineous parents. This patient had evolving CPHD, normal ACTH, APH and normal posterior pituitary (NPP). A previously reported patient homozygous for p.I26T had evolving CPHD and EPP. Finally, we identified compound heterozygous mutations in HESX1, p.[R159W];[R160H], in a patient with PA and CPHD. We showed that both of these mutations abrogate the ability of HESX1 to repress PROP1-mediated transcriptional activation. A patient homozygous for p.R160H was previously reported in a patient with CPHD, EPP, APH. Conclusion These three examples demonstrate that HESX1 mutations cause variable clinical features in patients, which suggests an influence of modifier genes or environmental factors on the phenotype.

Hypothyroidism is a cause of genetic and environmentally induced deafness. The sensitivity of cochlear development and function to thyroid hormone (TH) mandates understanding TH action in this sensory organ. Prop1(df) and Pou1f1(dw) mutant mice carry mutations in different pituitary transcription factors, each resulting in pituitary thyrotropin deficiency. Despite the same lack of detectable serum TH, these mutants have very different hearing abilities: Prop1(df) mutants are mildly affected, while Pou1f1(dw) mutants are completely deaf. Genetic studies show that this difference is attributable to the genetic backgrounds. Using embryo transfer, we discovered that factors intrinsic to the fetus are the major contributor to this difference, not maternal effects. We analyzed Prop1(df) mutants to identify processes in cochlear development that are disrupted in other hypothyroid animal models but protected in Prop1(df) mutants by the genetic background. The development of outer hair cell (OHC) function is delayed, but Prestin and KCNQ4 immunostaining appear normal in mature Prop1(df) mutants. The endocochlear potential and KCNJ10 immunostaining in the stria vascularis are indistinguishable from wild type, and no differences in neurofilament or synaptophysin staining are evident in Prop1(df) mutants. The synaptic vesicle protein otoferlin normally shifts expression from OHC to IHC as temporary afferent fibers beneath the OHC regress postnatally. Prop1(df) mutants exhibit persistent, abnormal expression of otoferlin in apical OHC, suggesting delayed maturation of synaptic function. Thus, the genetic background of Prop1(df) mutants is remarkably protective for most functions affected in other hypothyroid mice. The Prop1(df) mutant is an attractive model for identifying the genes that protect against deafness.

The absence of thyroid hormone (TH) during late gestation and early infancy can cause irreparable deafness in both humans and rodents. A variety of rodent models have been used in an effort to identify the underlying molecular mechanism. Here, we characterize a mouse model of secondary hypothyroidism, pituitary transcription factor 1 (Pit1dw), which has profound, congenital deafness that is rescued by oral TH replacement. These mutants have tectorial membrane abnormalities, including a prominent Hensen's stripe, elevated β-tectorin composition, and disrupted striated-sheet matrix. They lack distortion product otoacoustic emissions and cochlear microphonic responses, and exhibit reduced endocochlear potentials, suggesting defects in outer hair cell function and potassium recycling. Auditory system and hair cell physiology, histology, and anatomy studies reveal novel defects of hormone deficiency related to deafness: (1) permanently impaired expression of KCNJ10 in the stria vascularis ofPit1dwmice, which likely contributes to the reduced endocochlear potential, (2) significant outer hair cell loss in the mutants, which may result from cellular stress induced by the lower KCNQ4 expression and current levels inPit1dwmutant outer hair cells, and (3) sensory and strial cell deterioration, which may have implications for thyroid hormone dysregulation in age-related hearing impairment. In summary, we suggest that these defects in outer hair cell and strial cell function are important contributors to the hearing impairment inPit1dwmice.

The anterior and intermediate lobes of the pituitary gland are formed from Rathke’s pouch. FGF, BMP and WNT signals emanating from the ventral diencephalon influence pouch growth and development. In order to examine the role of canonical WNT signaling during pituitary development we examined the pituitary expression of the TCF/LEF family of transcription factors, which mediate WNT signaling through the binding of β-catenin. We report here the expression of several members of this family during pituitary development and the functional role of one member, TCF4 (TCF7L2), in the induction of the pituitary primordium. TCF4 is expressed in the ventral diencephalon early in pituitary development, rostral to a domain of BMP and FGF expression. Tcf4 deficient mice express Fgf10 and Bmp4; however, the Bmp and Fgf expression domains are expanded rostrally. As a result, additional pituitary progenitor cells are recruited into Rathke’s pouch in Tcf4 mutants. Mutants also exhibit an expansion of the Six6 expression domain within Rathke’s pouch, which may increase the number of proliferating pouch cells, resulting in a greatly enlarged anterior pituitary gland. This suggests that TCF4 negatively regulates pituitary growth through two mechanisms. The first mechanism is to restrict the domains of BMP and FGF signaling in the ventral diencephalon, and the second mechanism is the restriction of Six6 within Rathke’s pouch. Thus, TCF4 is necessary both intrinsically and extrinsically to Rathke’s pouch to ensure the proper growth of the pituitary gland.

Rathke’s pouch contains progenitor cells that differentiate into the endocrine cells of the pituitary gland. It gives rise to gonadotrope, thyrotrope, somatotrope, corticotrope and lactotrope cells in the anterior lobe and the intermediate lobe melanotropes. Pituitary precursor cells express many members of the Notch signaling pathway including the downstream effector gene Hes1. We hypothesized that Hes1 regulates the timing of precursor differentiation and cell fate determination. To test this idea, we expressed Hes1 in differentiating pituitary cells and found that it can inhibit gonadotrope and thyrotrope differentiation. Pituitaries of Hes1 deficient mice have anterior lobe hypoplasia. All cells in the anterior lobe are specified and differentiate, but an early period of increased cell death and reduced proliferation causes reduced growth, evident as early as e14.5. In addition, cells within the intermediate lobe differentiate into somatotropes instead of melanotropes. Thus, the Hes1 repressor is essential for melanotrope specification. These results demonstrate that Notch signaling plays multiple roles in pituitary development, influencing precursor number, organ size, cell differentiation and ultimately cell fate.

The LHX3 transcription factor plays critical roles in pituitary and nervous system development. Mutations in the human LHX3 gene cause severe hormone deficiency diseases. The gene produces two mRNAs which can be translated to three protein isoforms. The LHX3a protein contains a central region with LIM domains and a homeodomain, and a carboxyl terminus with the major transactivation domain. LHX3b is identical to LHX3a except that it has a different amino terminus. M2-LHX3 lacks the amino terminus and LIM domains of LHX3a/b. In vitro experiments have demonstrated these three proteins have different biochemical and gene regulatory properties. Here, to investigate the effects of overexpression of LHX3 in vivo, the alpha glycoprotein subunit (alphaGSU) promoter was used to produce LHX3a, LHX3b, and M2-LHX3 in the pituitary glands of transgenic mice. Alpha GSU-beta galactosidase animals were generated as controls. Male alphaGSU-LHX3a and alphaGSU-LHX3b mice are infertile and die at a young age as a result of complications associated with obstructive uropathy including uremia. These animals have a reduced number of pituitary gonadotrope cells, low circulating gonadotropins, and possible sex hormone imbalance. Female alphaGSU-LHX3a and alphaGSU-LHX3b transgenic mice are viable but have reduced fertility. By contrast, alphaGSU-M2-LHX3 mice and control mice expressing beta galactosidase are reproductively unaffected. These overexpression studies provide insights into the properties of LHX3 during pituitary development and highlight the importance of this factor in reproductive physiology.

ISLET1 is a homeodomain transcription factor necessary for development of the pituitary, retina, motor neurons, heart, and pancreas. Isl1-deficient mice (Isl1−/−) die early during embryogenesis at embryonic day 10.5 due to heart defects, and at that time, they have an undersized pituitary primordium. ISL1 is expressed in differentiating pituitary cells in early embryogenesis. Here, we report the cell-specific expression of ISL1 and assessment of its role in gonadotropes and thyrotropes. Isl1 expression is elevated in pituitaries of Cga−/− mice, a model of hypothyroidism with thyrotrope hypertrophy and hyperplasia. Thyrotrope-specific disruption of Isl1 with Tshb-cre is permissive for normal serum TSH, but T4 levels are decreased, suggesting decreased thyrotrope function. Inducing hypothyroidism in normal mice causes a reduction in T4 levels and dramatically elevated TSH response, but mice with thyrotrope-specific disruption of Isl1 have a blunted TSH response. In contrast, deletion of Isl1 in gonadotropes with an Lhb-cre transgene has no obvious effect on gonadotrope function or fertility. These results show that ISL1 is necessary for maximal thyrotrope response to hypothyroidism, in addition to its role in development of Rathke's pouch.

International audience; OTX2 is a homeodomain transcription factor that is necessary for normal head development in mouse and man. Heterozygosity for loss-of-function alleles causes an incompletely penetrant, haploinsufficiency disorder. Affected individuals exhibit a spectrum of features that range from developmental defects in eye and/or pituitary development to acephaly. To investigate the mechanism underlying the pituitary defects, we used different cre lines to inactivate Otx2 in early head development and in the prospective anterior and posterior lobes. Mice homozygous for Otx2 deficiency in early head development and pituitary oral ectoderm exhibit craniofacial defects and pituitary gland dysmorphology, but normal pituitary cell specification. The morphological defects mimic those observed in humans and mice with OTX2 heterozygous mutations. Mice homozygous for Otx2 deficiency in the pituitary neural ectoderm exhibited altered patterning of gene expression and ablation of FGF signaling. The posterior pituitary lobe and stalk, which normally arise from neural ectoderm, were extremely hypoplastic. Otx2 expression was intact in Rathke's pouch, the precursor to the anterior lobe, but the anterior lobe was hypoplastic. The lack of FGF signaling from the neural ectoderm was sufficient to impair anterior lobe growth, but not the differentiation of hormone-producing cells. This study demonstrates that Otx2 expression in the neural ectoderm is important intrinsically for the development of the posterior lobe and pituitary stalk, and it has significant extrinsic effects on anterior pituitary growth. Otx2 expression early in head development is important for establishing normal craniofacial features including development of the brain, eyes and pituitary gland.

Mutations in the transcription factors PIT1 (pituitary transcription factor 1) and PROP1 (prophet of Pit1) lead to pituitary hormone deficiency and hypopituitarism in mice and humans. To determine the basis for this, we performed histological analysis of Pit1- and Prop1-deficient dwarf mouse pituitaries throughout fetal and postnatal development. Pit1-deficient mice first exhibit pituitary hypoplasia after birth, primarily caused by reduced cell proliferation, although there is some apoptosis. To determine whether altered development of the vascular system contributes to hypopituitarism, we examined vascularization from embryonic d 14.5 and throughout development. No obvious differences in vascularization are evident in developing Pit1-deficient pituitaries. In contrast, the Prop1-deficient mouse pituitaries are poorly vascularized and dysmorphic, with a striking elevation in apoptosis. At postnatal d 11, apoptosis-independent caspase-3 activation occurs in thyrotropes and somatotropes of normal but not mutant pituitaries. This suggests that Prop1 and/or Pit1 may be necessary for caspase-3 expression. These studies provide further insight as to the mechanisms of Prop1 and Pit1 action in mice.

The shaker2 (sh2) mouse is a murine model for human non-syndromic deafness DFNB3. The mice have abnormal circling behavior suggesting a balanced disorder, and profound deafness. The insertion of a bacterial artificial chromosome (BAC) transgene containing the Myo15a gene into sh2/sh2 zygotes confers hearing capability and abolishes the circling behavior in 1-month-old transgenic animals. In this study, we investigated both the hearing and the morphology of the cochlea in Myo15a mutants carrying this BAC transgene at two, four, or six months of age. The hearing threshold of these mice is normal, with no physiologically significant differences compared to age-matched heterozygous sh2J mice (with or without the BAC transgene). In six-month-old transgenic mice with the BAC, the morphology of hair cells in the apical and upper basal turns of the cochlea is normal. Hair cells of lower basal turn, however, were missing in some mutant animals. This study demonstrates that BAC transgene correction cannot only maintain normal morphology but also confer stable hearing function in Myo15a mutant mice for as long as 6 months. In addition, excess Myo15a expression has no physiologically significant protective or deleterious effects on hearing of normal mice, suggesting that the dosage of Myo15a may not be problematic for gene therapy.

The PITX family of transcription factors regulate the development of many organs. Pitx1 mutants have a mild pituitary phenotype, but Pitx2 is necessary for the development of Rathke's pouch, expression of essential transcription factors in gonadotropes, and expansion of the Pit1 lineage. We report that lack of Pitx2 causes the pouch to undergo excessive cell death, resulting in severe pituitary hypoplasia. Transgenic overexpression of PITX2 in the pituitary can increase the gonadotrope population, suggesting that the absolute concentration of PITX2 is important for normal pituitary cell lineage expansion. We show that PITX1 and PITX2 proteins are present in similar expression patterns throughout pituitary development and in the mature pituitary. Both transcription factors are preferentially expressed in adult gonadotropes and thyrotropes, suggesting the possibility of overlap in maintenance of adult pituitary functions within these cell types. Double knockouts of Pitx1 and Pitx2 exhibit severe pituitary hypoplasia and fail to express the transcription factor LHX3. This indicates that these PITX genes are upstream of Lhx3 and have compensatory roles during development. Thus, the combined dosage of these PITX family members is vital for pituitary development, and their persistent coexpression in the adult pituitary suggests a continued role in maintenance of pituitary function.

To study the effects of premature and chronic ligand-mediated luteinizing hormone receptor (LHR) activation on reproductive development, we have generated transgenic mice expressing a genetically engineered, constitutively active yoked hormone–receptor complex (YHR), in which a fusion protein of human chorionic gonadotropin (hCG) is covalently linked to the N-terminus of rat LHR. YHR-expressing mice (YHR+) were analyzed at pre- and post-pubertal ages. Relative to wild type (WT) controls, male mice exhibited prepubertal increases in testosterone levels and seminal vesicle weights, and decreases in serum FSH, serum LH, testes weight, and the size of the seminiferous tubules. In adult male YHR+ mice, testosterone and LH levels are not significantly different from WT controls. However, FSH levels and testes weights remain decreased. Female YHR+ mice undergo precocious puberty with early vaginal opening, accelerated uterine development, enhanced follicular development, including the presence of corpora lutea, and an increase in serum progesterone. At 12 weeks of age, the ovary exhibits a relative increase in the amount of interstitial tissue, comprised of cells that are hypertrophic and luteinized, as well as follicles that are degenerating. Additionally, hemorrhagic cysts develop in approximately 25% of the transgenic mice. These degenerative changes are consistent with an aging ovary suggesting that CG-induced LHR activation in female mice leads to precocious sexual development and ovarian lesions. Taken together, these data indicate that the single chain YHR is functional in vivo and demonstrate that YHR+ mice provide a novel system to further understand the reproductive consequences of aberrant LHR activation.

Mutations in the PROP1 transcription factor gene lead to reduced production of thyrotropin, GH, prolactin, and gonadotropins as well as to pituitary hypoplasia in adult humans and mice. Some PROP1-deficient patients initially exhibit pituitary hyperplasia that resolves to hypoplasia. To understand this feature and to explore the mechanism whereby PROP1 regulates anterior pituitary gland growth, we carried out longitudinal studies in normal and Prop1-deficient dwarf mice from early embryogenesis through adulthood, examining the volume of Rathke’s pouch and its derivatives, the position and number of dividing cells, the rate of apoptosis, and cell migration by pulse labeling. The results suggest that anterior pituitary progenitors normally leave the perilumenal region of Rathke’s pouch and migrate to form the anterior lobe as they differentiate. Some of the cells that seed the anterior lobe during organogenesis have proliferative potential, supporting the expansion of the anterior lobe after birth. Prop1-deficient fetal pituitaries are dysmorphic because mutant cells are retained in the perilumenal area and fail to differentiate. After birth, mutant pituitaries exhibit enhanced apoptosis and reduced proliferation, apparently because the mutant anterior lobe is not seeded with progenitors. These studies suggest a mechanism for Prop1 action and an explanation for some of the clinical findings in human patients.

Pitx2, a homeodomain transcription factor, is essential for normal development of the pituitary gland, craniofacial region, eyes, heart, abdominal viscera, and limbs. Complete loss of Pitx2 in mice (Pitx2(-/-)) results in embryonic lethality by approximately e15 due to cardiac defects, whereas embryos with partial loss of function (Pitx2(neo/-) or Pitx2(neo/neo)) survive until later in development (e17-e19). Pitx2 is expressed in discrete populations of postmitotic neurons in the mouse brain, but its role in mammalian central nervous system (CNS) development is not known. We undertook an analysis of Pitx2-deficient embryos to determine whether loss of Pitx2 affects CNS development. The CNS is normal in hypomorphic e16.5 Pitx2(neo/-) and e18.5 Pitx2(neo/neo) embryos, with no evidence of midline or other defects. Midgestation (e10.5) Pitx2(-/-) embryos have normally formed neural tube structures and cerebral vesicles, whereas older (e14.5) Pitx2(-/-) embryos exhibit loss of gene expression and axonal projections in the subthalamic nucleus (a group of cells in the ventrolateral thalamus) and in the developing superior colliculus of dorsal midbrain. Our results suggest a role for Pitx2 in regulating regionally specific terminal neuronal differentiation in the developing ventrolateral thalamus and midbrain.

Mutations in the prophet of PIT1 gene (PROP1) are the most common cause of multiple pituitary hormone deficiency in humans; however, the mechanism of PROP1 action is not well understood. We report that Prop1 is essential for dorsally restricted expression of a Groucho-related gene, transducin-like enhancer of split 3 (Tle3), which encodes a transcriptional corepressor. Deficiency of a related gene, amino terminal enhancer of split (Aes), causes pituitary anomalies and growth insufficiency. TLE3 and AES have been shown to interact with TCF/LEF (transcripiton factors of the T cell-specific and lymphoid enhancer specific group) family members in cell culture systems. In the absence of TCF4 (Tcf7L2), Prop1 levels are elevated, pituitary hyperplasia ensues and palate closure is abnormal. Thus, we demonstrate that Tcf4 and Aes influence pituitary growth and development, and place Tcf4 and Tle3 in the genetic hierarchy with Prop1.

Knockout mice lacking the orphan nuclear receptor steroidogenic factor 1 (SF1) exhibit a complex endocrine phenotype that includes adrenal and gonadal agenesis, impaired expression of pituitary gonadotropins, and absence of the ventromedial hypothalamic nucleus (VMH). These multiple defects complicate efforts to delineate primary versus secondary effects of SF1 deficiency in different tissues, such that its direct role in gonadotropes remains uncertain. To define this role, we have expressed Cre recombinase driven by the promoter region of the common α subunit of glycoprotein hormones (αGSU), thereby inactivating a loxP-modified SF1 locus in the anterior pituitary gland. Although pituitary-specific SF1 knockout mice were fully viable, they were sterile and failed to develop normal secondary sexual characteristics. Their adrenal glands and VMH appeared normal histologically, but their testes and ovaries were severely hypoplastic. αGSU-Cre, loxP mice had normal levels of most pituitary hormones, but had markedly decreased expression of LH and FSH. Treatment with exogenous gonadotropins stimulated gonadal steroidogenesis, inducing germ cell maturation in males and follicular and uterine maturation in females – establishing that the gonads can respond to gonadotropins. The pituitary-specific SF1 knockout mice are a novel genetic model of hypogonadotropic hypogonadism that establishes essential role(s) of SF1 in pituitary gonadotropes.

Pitx2 is a homeodomain transcription factor that is mutated in Rieger syndrome, a haploinsufficiency disorder affecting eyes and teeth. Pitx2 also has a postulated role in left-right axis determination. We assessed the requirements for Pitx2 directly by generating hypomorphic and null alleles. Heterozygotes for either allele have eye abnormalities consistent with Rieger syndrome. The ventral body wall fails to close in embryos homozygous for the null allele, leaving the heart and abdominal organs externalized and the body axis contorted. In homozygotes for either allele, the heart tube undergoes normal, rightward looping and the stomach is positioned normally. In contrast, homozygotes for both alleles exhibit right isomerization of the lungs. Thus, Pitx2 is required for left-right asymmetry of the lungs but not other organs. Homozygotes for either allele exhibit septal and valve defects, and null homozygotes have a single atrium proving that a threshold level of Pitx2 is required for normal heart development. Null homozygotes exhibit arrest of pituitary gland development at the committed Rathke pouch stage and eye defects including optic nerve coloboma and absence of ocular muscles. This allelic series establishes that Pitx2 is required for the development of mulitple organs in a dosage-sensitive manner.

Corticotropin-releasing hormone (CRH) is widely recognized as the primary mediator of the neuroendocrine and behavioral responses to stress, including stress-induced anxiety. The biological activity of CRH and other mammalian CRH-like peptides, such as urocortin, may be modulated by CRH-binding protein (CRH-BP). To assess directly the CRH-BP function, we created a mouse model of CRH-BP deficiency by gene targeting. Basal adrenocorticotropic hormone and corticosterone levels are unchanged in the CRH-BP-deficient mice, and the animals demonstrate a normal increase in adrenocorticotropic hormone and corticosterone after restraint stress. In contrast, adult male CRH-BP-deficient mice show significantly reduced body weight when compared with wild-type controls. CRH-BP-deficient mice also exhibit a significant increase in anxiogenic-like behavior as assessed by the elevated plus maze and defensive withdrawal tests. The increased anorectic and anxiogenic-like behavior most likely is caused by increased “free” CRH and/or urocortin levels in the brain of CRH-BP-deficient animals, suggesting an important role for CRH-BP in maintaining appropriate levels of these peptides in the central nervous system.

Humans with mutations in SOX3 have panhypopituitarism, but the developmental mechanisms underlying this defect are unknown. Conditional disruption of Sox3 in mice now suggests that anterior pituitary development depends on Sox3 expression in the overlying neural ectoderm, which establishes midline structures and regulates production of inductive BMP and FGF signals.

We discovered a new spontaneous mutant allele of Npr2 named peewee (pwe) that exhibits severe disproportionate dwarfism and female infertility. The pwe phenotype is caused by a four base-pair deletion in exon 3 that generates a premature stop codon at codon 313 (L313X). The Npr2(pwe/pwe) mouse is a model for the human skeletal dysplasia acromesomelic dysplasia, Maroteaux type (AMDM). We conducted a thorough analysis of the female reproductive tract and report that the primary cause of Npr2(pwe/pwe) female infertility is premature oocyte meiotic resumption, while the pituitary and uterus appear to be normal. Npr2 is expressed in chondrocytes and osteoblasts. We determined that the loss of Npr2 causes a reduction in the hypertrophic and proliferative zones of the growth plate, but mineralization of skeletal elements is normal. Mutant tibiae have increased levels of the activated form of ERK1/2, consistent with the idea that natriuretic peptide receptor type 2 (NPR2) signaling inhibits the activation of the MEK/ERK mitogen activated protein kinase pathway. Treatment of fetal tibiae explants with mitogen activated protein kinase 1 and 2 inhibitors U0126 and PD325901 rescues the Npr2(pwe/pwe) growth defect, providing a promising foundation for skeletal dysplasia therapeutics.

Ames dwarf mice have a recessive defect that results in affected mice (df/df) with extremely hypocellular anterior pituitaries that generally lack somatotropes, lactotropes, and thyrotropes. We report detection of rare foci of GH+ cells by immunocytochemistry, suggesting that some commitment to a somatotrope cell fate can occur in the pituitaries of df/df mice. A role for GHRF in regulating somatotrope proliferation is well documented. It has been shown that expression of human GHRF (hGHRF) in transgenic mice resulted in increased somatic growth and somatotrope hyperplasia over nontransgenic littermates. To assess whether overexpression of GHRF during ontogeny might elicit a physiological response in df/df mice, we generated df/df mice expressing the hGhrf transgene. Although the somatic growth of transgenic df heterozygotes was dramatically increased over that of nontransgenic littermates, df/df mice were refractory to excess GHRF. No GHRF receptor (Grfr) transcripts were detectable in df/df fetuses or adult mice by in situ hybridization analysis. In contrast, Grfr expression is detected by e16.5 in df/+ mice. The lack of Grfr expression in df/df fetuses may account for their lack of response to GHRF and implies that the df gene product is required before e16.5.

Transient transfection studies have proven useful in unraveling the molecular mechanisms underlying gonadotrope-specific expression and hormonal regulation of the gene encoding the alpha-subunit of the glycoprotein hormones. In contrast, similar studies performed with the LH beta gene have been less informative. When assayed by transient transfection into alpha T3-1 cells, activity of a 776-basepair bovine LH beta promoter-chloramphenicol acetyltransferase fusion gene (bLH beta CAT) was no greater than that of a promoterless control. To determine whether limited activity in vitro reflected the absence of critical regulatory elements, we examined activity of bovine LH beta fusion genes after stable integration in transgenic mice. In contrast to transient transfection studies, the LH beta promoter targeted high levels of CAT expression specifically to the pituitary. In addition, a bLH beta TK fusion gene was active only in gonadotropes. The bLH beta CAT transgene was also evaluated for responsiveness to gonadal steroids and GnRH. Testosterone and 17 beta-estradiol were capable of suppressing activity 70-80% in castrated males, despite the absence of high affinity binding sites for androgen or estrogen receptors. This suggests that feedback inhibition of LH beta CAT transgene expression by gonadal steroids may occur through an indirect mechanism, possibly at the level of the hypothalamus. To address whether the bLH beta CAT transgene could be regulated by GnRH, we treated ovariectomized females with antide, a GnRH antagonist. Antide suppressed transgene activity by 60%. Thus, the proximal promoter of the bovine LH beta subunit gene directs appropriate patterns of cell-specific expression and retains responsiveness to gonadal steroids and GnRH. In light of the robust activity of the LH beta promoter in transgenic mice, we suggest that this animal model can be exploited further to dissect the complex mechanisms that underlie gonadotrope-specific expression and hormonal regulation of the LH beta gene.

CRH mRNA was detected by in situ hybridization histochemistry in numerous regions of the adult mouse brain, including most prominently the paraventricular nucleus (PVN) of the hypothalamus, the inferior olivary nucleus, and Barrington's nucleus. After adrenalectomy, steady state CRH mRNA levels increased 1.7-fold, specifically in the PVN, consistent with reports of negative glucocorticoid regulation of CRH expression in the rat PVN. Ontogenetic analysis of CRH expression in fetal and neonatal mouse brain demonstrated CRH mRNA in PVN, Barrington's nucleus, olivary complex, and amygdaloid primordia on embryonic day 13.5. In contrast, CRH mRNA was not detectable in the cortex until after birth. CRH expression also exhibited differential regulation in ontogeny. CRH mRNA reached adult levels at markedly different times of development in each brain region, and CRH expression was reduced specifically in the PVN just before birth and the stress hyporesponsive period. High levels of CRH mRNA were present transiently in the developing lung and celiac ganglion. The novel findings of CRH expression in fetal lung during the period of glucocorticoid-induced lung maturation and in celiac ganglion during development of the sympathetic nervous system indicate that CRH may have some important developmental functions in addition to its role in activation of the stress response.

The neurologic mutant mouse, oscillator, is characterized by a fine motor tremor and muscle spasms that begin at 2 weeks of age and progressively worsen, resulting in death by 3 weeks of age. We report the localization of the oscillator mutation to the central region of mouse Chr 11, and demonstrate its allelism with spasmodic, a recessive viable neurological mutation which displays excessive startle. Oscillator is caused by a microdeletion in the gene coding for the alpha 1 subunit of the adult glycine receptor (Glra1). Glra1 assembles into a pentameric complex with the beta subunit of the glycine receptor (3 alpha (1)2 beta 5) to form a glycine-gated chloride channel. This receptor is the major adult glycine receptor, and the site of action of the poison strychnine. The oscillator deletion causes a frameshift resulting in loss of the highly conserved third cytoplasmic loop and fourth transmembrane domain of the protein. Membranes isolated from oscillator homozygote spinal cords display a 90% reduction in glycine-displaceable strychnine binding. This lack of ligand binding function confirms that oscillator is a complete loss of function allele. The oscillator mutation provides evidence that although at least four different alpha subunits exist for the glycine receptor, none of the other subunits can compensate for the loss of alpha 1 function. Mutations which impair GLRA1 function in humans have been shown to cause dominant familial startle disease. The identification of the oscillator mutation suggests that severe loss of function alleles in humans would result in prenatal or neonatal lethality.