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Limitations of the recognition elements in terms of synthesis, cost, availability, and stability have impaired the translation of biosensors into practical use. Inspired by nature to mimic the molecular recognition of the anti-SARS-CoV-2 S protein antibody (Ab

Context: Congenital hypopituitarism is a genetically heterogeneous condition. Whole exome sequencing (WES) is a promising approach for molecular diagnosis of patients with this condition. Objectives: To conduct WES in a patient with congenital hypopituitarism born to consanguineous parents, CDH2 screening in a cohort of patients with congenital hypopituitarism, and functional testing of a novel CDH2 variant. Design: Genomic DNA from a proband and her consanguineous parents was analyzed by WES. Copy number variants were evaluated. The genetic variants were filtered for population frequency (ExAC, 1000 genomes, gnomAD and ABraOM), in silico prediction of pathogenicity, and gene expression in pituitary and/or hypothalamus. Genomic DNA from 145 patients was screened for CDH2 by Sanger sequencing. Results: One female patient with deficiencies in GH, TSH, ACTH, LH, and FSH and ectopic posterior pituitary gland contained a rare homozygous c.865G>A (p.Val289Ile) variant in CDH2. To determine whether the p.Val289Ile variant in CDH2 affects cell adhesion properties, we stably transfected L1 fibroblast lines, labeled the cells with lipophilic dyes, and quantified aggregation. Large aggregates formed in cells expressing wild type CDH2, but aggregation was impaired in cells transfected with variant CDH2 or non-transfected. Conclusion: A homozygous CDH2 allelic variant was found in 1 hypopituitarism patient, and the variant impaired cell aggregation function in vitro. No disease-causing variants were found in 145 other patients screened for CDH2 variants. Thus, CDH2 is a candidate gene for hypopituitarism that needs to be tested in different populations.

Along with the growing number of laboratories that work with zebrafish (Danio rerio), it is necessary to have animals with good sanitary quality. Specific pathogens can interfere with the experimental results and in the life quality of the animals. Pseudoloma neurophilia is a parasite with high potential for interference in behavioural, morphology, toxicological and genetic research, and is very common in zebrafish facilities. With that, we implemented a protocol for the pathogen elimination in a genetically modified lineage (prop 1) using eggs from specific pathogen-free (SPF) wild-type fish (AB line) for in vitro fertilization, along with water recirculation equipment disinfection, appropriate PCR screening and back crossing protocols. This resulted in SPF prop 1 heterozygotes, which allowed us to move forward with subsequent crossings to develop homozygote prop 1 mutants for our research. Hence, this demonstrates a useful strategy for an individual research laboratory to rederive a specific mutant free line that is not available from other SPF laboratories.

Central adrenal insufficiency (CAI) is a life-threatening disorder. This occurs when ACTH production is insufficient, leading to low cortisol levels. Since corticosteroids are crucial to many metabolic responses under organic stress and inflammatory conditions, CAI recognition and prompt treatment are vital. However, the diagnosis of CAI is challenging. This is not only because its clinical presentation is usually oligosymptomatic, but also because the CAI laboratory investigation presents many pitfalls. Thus, the clarification of when to use each test could be helpful in many contexts. The CAI challenge is also involved in treatment: Several formulations of synthetic steroids exist, followed by the lack of a biomarker for glucocorticoid replacement. This review aims to access all available literature to synthesize important topics about who should investigate CAI, when it should be suspected, and how CAI must be treated.

Introduction The Ames strain, a spontaneous mutant mouse of the Prop1 gene, is deficient in GH, TSH, PRL and gonadotropins. In recent years, it has been the focus of studies on aging and there is a growing interest in elucidating the role of hormone replacement (HR) in the hypothalamic-pituitary-gonadal (HPG) axis. Aim The present study aimed to characterize sexual maturation and fertility restoration in isogenic strain under or not HR. Material and methods Five homozygous male animals were treated via intraperitoneal injections, starting 30 days postnatally, with levothyroxine 3x/week and recombinant human GH 5x/week for 40 days, followed by maintenance applications of both hormones once a week until they complete 90 days post natal. The sexual maturity was evaluated looking for balanoprepucial opening and descendent testis comparing untreated homozygous (n=5) with their wild type siblings (n=5). Fertility was evaluated by mating known fertile wild type animals with treated and untreated animals for 8 times. Reproductive parameters were evaluated between groups using histological sections of the testes (HE) and classified according to johnsen score where 1-2 was classified as absent germline cells and 8-10 normal development. At the sacrifice, testicular weight was measured using scale and spermogram was done looking for motility and viability in the sperm collected in the seminiferous tube. Gata2 transcription factor and pituitary hormones Lh, Fsh, Tsh, Prl and Gh transcriptional analysis were performed by RT-qPCR. Results The homozygous treated animals presented a 2 weeks delay in the age of sexual maturation compared to wild animals. Their fertility and reproductive parameters were restored noticed by increased testicular weight, improved spermatogenesis, similar morphology of seminiferous tubules (johnsen score 8.7) and spermogram compared to the wild type, besides presenting offspring when mated to their wild siblings. Sexual maturity was absent in most of the untreated homozygous animals presenting no offspring. The reproductive parameters in the untreated homozygous animals presented reduced testicular weight, size of seminiferous tubes leading to johnsen score as 5 and an azospermic spermogram in all animals. Interestingly 2 untreated homozugous animal had spontaneous maturation. Gata2 was significant decreased in the untreated animal (0,49 ± 0,19) compared to wild type (1 ± 0,15) (p≤ 0.019). LH transcriptional pattern was significant increase in the animals under treatment (1.56 ± 0.68) compared to homozygotes without hormonal intervention (0.36 ± 0.34) (p≤ 0.048). Conclusion Ames mutant mice under treatment with GH and levothyroxine replacement reached sexual maturation and restored fertility and the mechanics behind this phenomenon will be explored using RNA seq in the future. Presentation: Sunday, June 12, 2022 11:45 a.m. - 12:00 p.m.

To evaluated the metabolic profiles and vascular properties in congenital growth hormone (GH) deficiency (GHD) and its replacement in adults. Cross-sectional study conducted in a single tertiary center for pituitary diseases. Eighty-one adult subjects were divided into three groups: (1) 29 GHD patients with daily subcutaneous GH replacement therapy (GHRT) during adulthood; (2) 20 GHD patients without GHRT during adulthood and (3) 32 controls. Only patients with adequate adherence to others pituitary hormone deficiencies were included. Anthropometric parameters, body composition by dual-energy X-ray absorptiometry, metabolic profiles and vascular properties (carotid intima media thickness, pulse wave velocity and flow-mediated dilation) were compared among the groups. Waist-to-height ratio (WHR), body fat percentages and fat mass index (FMI) were lower in patients with GHRT than patients without GHRT during adulthood (0.49 ± 0.06 vs. 0.53 ± 0.06 p = 0.026, 30 ± 10 vs. 40 ± 11 p = 0.003 and 7.3 ± 4 vs. 10 ± 3.5 p = 0.041, respectively). In addition, association between longer GHRT and lower body fat percentage was observed (r = − 0.326, p = 0.04). We found higher triglyceride (113.5 ± 62 vs. 78 ± 36, p = 0.025) and lower HDL cholesterol (51 ± 17 vs. 66 ± 23, p = 0.029) levels in patients without GHRT during adulthood in comparison to controls. No statistical differences were observed for vascular properties among the groups. No differences in vascular properties were observed in congenital GHD adult patients with or without GHRT despite patients without GHRT had an unfavorable body composition. GHRT currently remains an individualized decision in adults with GHD and these findings bring new insight into the treatment and follow-up of these patients.

Despite the significant increase in the generation of SARS-CoV-2 contaminated domestic and hospital wastewater, little is known about the ecotoxicological effects of the virus or its structural components in freshwater vertebrates. In this context, this study evaluated the deleterious effects caused by SARS-CoV-2 Spike protein on the health of Danio rerio, zebrafish. We demonstrated, for the first time, that zebrafish injected with fragment 16 to 165 (rSpike), which corresponds to the N-terminal portion of the protein, presented mortalities and adverse effects on liver, kidney, ovary and brain tissues. The conserved genetic homology between zebrafish and humans might be one of the reasons for the intense toxic effects followed inflammatory reaction from the immune system of zebrafish to rSpike which provoked damage to organs in a similar pattern as happen in severe cases of COVID-19 in humans, and, resulted in 78,6% of survival rate in female adults during the first seven days. The application of spike protein in zebrafish was highly toxic that is suitable for future studies to gather valuable information about ecotoxicological impacts, as well as vaccine responses and therapeutic approaches in human medicine. Therefore, besides representing an important tool to assess the harmful effects of SARS-CoV-2 in the aquatic environment, we present the zebrafish as an animal model for translational COVID-19 research., Graphical abstract Unlabelled Image

Three open-source anti-kinetoplastid chemical boxes derived from a whole-cell phenotypic screening by GlaxoSmithKline (Tres Cantos Anti-Kinetoplastid Screening, TCAKS) were exploited for the discovery of a novel core structure inspiring new treatments of parasitic diseases targeting the trypansosmatidic pteridine reductase 1 (PTR1) and dihydrofolate reductase (DHFR) enzymes. In total, 592 compounds were tested through medium-throughput screening assays. A subset of 14 compounds successfully inhibited the enzyme activity in the low micromolar range of at least one of the enzymes from both Trypanosoma brucei and Lesihmania major parasites (pan-inhibitors), or from both PTR1 and DHFR-TS of the same parasite (dual inhibitors). Molecular docking studies of the protein–ligand interaction focused on new scaffolds not reproducing the well-known antifolate core clearly explaining the experimental data. TCMDC-143249, classified as a benzenesulfonamide derivative by the QikProp descriptor tool, showed selective inhibition of PTR1 and growth inhibition of the kinetoplastid parasites in the 5 μM range. In our work, we enlarged the biological profile of the GSK Kinetobox and identified new core structures inhibiting selectively PTR1, effective against the kinetoplastid infectious protozoans. In perspective, we foresee the development of selective PTR1 and DHFR inhibitors for studies of drug combinations.

Introduction Zebrafish has been used as an animal model to study human disease due to its 75% genetic homology with humans besides easier maintenance, small size and high reproductive rate. knockout Gene through CRISPR/Cas genomic edition can lead to an inactivating protein due to frameshift and stop codon, while Knockin allows a specific base edition. Whole exome sequence allows the identification of new/rare variants as molecular diagnosis in patients with congenital hypopituitarism (CH), although sometimes phenotype-genotype is mandatory and edited zebrafish genome can be a tool. The aims of this work was to generate the gh1 knockout gene in zebrafish, mimetizing a patient with CH harboring GH1 c.171delT (p.Phe57Leufs*43) allelic variant leading to frameshift and stop codon and cdh2 knockin due to CDH2 c.865G>A (p.Val289Ile) allelic variant in homozygosity in a patient with CH. Methods For the gh1 knockout gene 2 different guides (sgRNA) were designed in exon 5. At one cell stage a total number of 274 embryos were injected with different sgRNA and Cas9. At 3 months after fertilization, 12 animals had their tail DNA extracted followed by PCR amplification with primers flanking exon 5 and the product was Sanger sequenced. For the cdh2 knockin g>a for p.Val289Ile, base editing plasmid was used, containing an inserted DNA with cytidine deaminase fused to Cas9 nickase (nCas9), that direct convert C to T or G to A in the Zebrafish DNA sequence of interest. Twenty-four hours after injection, a total of 100 embryo's DNA were collected and extracted followed by PCR amplification and Sanger sequenced in order to check mutagenesis efficiency. Results For the gh1 knockout gene animals that reached sexual maturity, two of them with an allelic variant leading to frameshift and stop codon (animal 1 harboring ENSDARG00000038185: g.568_572del, animal 2 harboring ENSDARG00000038185: g.554_560insACGAACG) were prioritized for the strains construction. These animals (F0) were mated with WT animals and their offspring (F1) were genotyped, showing mutations not seen in the tail sequencing of the parents, suggesting a gonadal mosaic in F0 generation. At 3 months these animals (F1) were mated and F2 offspring with pure heterozygous mutation were generated and crossed with WT in order to obtain the mendelian rate of WT, HT and Homo to characterize the animal phenotype. From 100 animals injected for cdh2 knockin approach, 10 random animals have already been sequenced and presented no expected pathogenic allelic variant. Conclusion The genomic editing technique by Crispr cas was efficient to generate a pure heterozygous gh1 knockout animal in order to obtain homozygous animal in F3 for phenotype characterization, while knockin was inefficient for the analyzed number of eggs although it is missing 90 animal to be analyzed in order to calculate the real technique efficiency. Presentation: Sunday, June 12, 2022 12:30 p.m. - 12:35 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Introduction An intact GH-IGF-1 axis is known to be essential for proper growth. However, cases in which individuals with growth hormone deficiency (GHD) reach target height without the use of GH suggest that other mechanisms may play a role in the growth process. Out of 209 patients with hypopituitarism followed in the endocrinology clinic at HCFMUSP, 9 presented with normal stature despite GHD and hypogonadotropic hypogonadism. Among them, 1 male patient presented with tall stature. The mechanisms under growth without growth hormone are poorly understood, so we hypothesized that genetic mutations in genes related to tall stature could be a plausible explanation. The aim of the present work was to look for allelic variants in the exome that could be associated with tall stature, combined pituitary hormone deficiency and/or skeletal deformities. The index male patient presented at the age of 28 to a medical assistance due to the lack of pubertal development, leading to the diagnosis of FSH/LH and TSH deficiencies and thus treated accordingly. He was still growing even under testosterone replacement and noticed that his hand and fingers also got bigger in this period. At 32-year-old he presented to our service with a stature of 193.5cm (z score of +2.40) being out of his target height range. An arm span of 195cm was notice together with skeletal deformities such as claw toes, trigger fingers in hands and a barrel chest. At this time ACTH and GH deficiencies were diagnosed and an adult dose of GH was initiated. Over one year treatment he grew 1 cm even presenting complete closed epiphyses in hands but incomplete epiphyseal fusion in the iliac crest (Risser 4). In the skeletal X ray scoliosis, deformities in hands and feet were noticed. Pituitary MRI revealed an ectopic neurohypophysis and a reduced adenohypophysis. Whole exome sequencing was performed and allelic variants in exonic or splice site regions with frequency of less than 1% were prioritized. Out of 26 variants, 13 were classified as VUS or pathogenic in the genes PSG4, ZGPAT, LRP2, LRP5, LRP6, RYR1, REL SPAST, SDHC, EGFR, ARID3B and TGFB2, being the last 5 genes never described in 4 different populational databases (gnomAD, 1000G, ABraOM and SELAdb). Allelic variant in TGFB2 gene has been related to Marfan syndrome. Family members are having these genes in the process of being segregated. Conclusion Mutations in genes related to tall stature may be a mechanism that could explains normal growth among individuals with GHD. Presentation: Sunday, June 12, 2022 12:42 p.m. - 12:47 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Along with the growing number of laboratories that work with zebrafish (Danio rerio), it is necessary to have animals with good sanitary quality. Specific pathogens can interfere with the experimental results and in the life quality of the animals. Pseudoloma neurophilia is a parasite with high potential for interference in behavioural, morphology, toxicological and genetic research, and is very common in zebrafish facilities. With that, we implemented a protocol for the pathogen elimination in a genetically modified lineage (prop 1) using eggs from specific pathogen-free (SPF) wild-type fish (AB line) for in vitro fertilization, along with water recirculation equipment disinfection, appropriate PCR screening and back crossing protocols. This resulted in SPF prop 1 heterozygotes, which allowed us to move forward with subsequent crossings to develop homozygote prop 1 mutants for our research. Hence, this demonstrates a useful strategy for an individual research laboratory to rederive a specific mutant free line that is not available from other SPF laboratories.

Context Androgen insensitivity syndrome (AIS) is the most common cause of disorders of sex development in 46,XY individuals. It is an X-linked condition usually caused by pathogenic allelic variants in the androgen receptor (AR) gene. The phenotype depends on the AR variant, ranging from severe undervirilization (complete AIS) to several degrees of external genitalia undervirilization. Although 90% of those with complete AIS will have AR mutations, this will only be true for 40% of those with partial AIS (PAIS). Objective To identify the genetic etiology of AIS in a large multigenerational family with the PAIS phenotype. Participants Nine affected individuals with clinical and laboratory findings consistent with PAIS and a normal exonic AR sequencing Settings Endocrine clinic and genetic institute from two academic referral centers Design Analysis of whole exons of the AR gene, including splicing regions, was performed, followed by sequencing of the 5′untranslated region (UTR) of the AR gene. Detailed phenotyping was performed at the initial diagnosis and long-term follow-up, and circulating levels of steroid gonadal hormones were measured in all affected individuals. AR expression was measured using RT-PCR and cultured fibroblasts. Results All 46,XY family members with PAIS had inherited, in hemizygosity, a complex defect (∼1100 bp) in the 5′UTR region of the AR surrounded by a duplicated 18-bp sequence (target site duplication). This sequence is 99.7% similar to an active, long, interspersed element present on the X chromosome (AC002980; Xq22.2), which was inserted in the 5′UTR of the AR gene, severely reducing AR expression and leading to PAIS. Conclusion The molecular diagnosis of PAIS remains challenging. The genomic effect of retrotransposon mobilization should be considered a possible molecular cause of AIS and other AR diseases.

The first description of patients with combined pituitary hormone deficiencies (CPHD) caused by PROP1 mutations was made 20 years ago. Here we updated the clinical and genetic characteristics of patients with PROP1 mutations and summarized the phenotypes of 14 patients with 7 different pathogenic PROP1 mutations followed at the Hospital das Clínicas of the University of Sao Paulo. In addition to deficiencies in GH, TSH, PRL and gonadotropins some patients develop late ACTH deficiency. Therefore, patients with PROP1 mutations require permanent surveillance. On magnetic resonance imaging, the pituitary stalk is normal, and the posterior lobe is in the normal position. The anterior lobe in patients with PROP1 mutations is usually hypoplastic but may be normal or even enlarged. Bi-allelic PROP1 mutations are currently the most frequently recognized genetic cause of CPHD worldwide. PROP1 defects occur more frequently among offspring of consanguineous parents and familial cases, but they also occur in sporadic cases, especially in countries in which the prevalence of PROP1 mutations is relatively high. We classified all reported PROP1 variants described to date according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) guidelines: 29 were pathogenic, 2 were likely pathogenic, and 2 were of unknown significance. An expansion of the phenotype of patients with PROP1 mutations was observed since the first description 20 years ago: variable anterior pituitary size, different pathogenic mutations, and late development of ACTH deficiency. PROP1 mutations are the most common cause of autosomal recessive CPHD with a topic posterior pituitary lobe. Arch Endocrinol Metab. 2019;63(2):167-74

Aim Congenital hypopituitarism has an incidence of 1:3500–10,000 births and is defined by the impaired production of pituitary hormones. Early diagnosis has an impact on management and genetic counselling. The clinical and genetic heterogeneity of hypopituitarism poses difficulties to select the order of genes to analyse. The objective of our study is to screen hypopituitarism genes (candidate and previously related genes) simultaneously using a target gene panel in patients with congenital hypopituitarism. Methods Screening of 117 subjects with congenital hypopituitarism for pathogenic variants in 26 genes associated with congenital hypopituitarism by massively parallel sequencing using a customized target gene panel. Results We found three novel pathogenic variants in OTX2 c.295C>T:p.Gln99*, GLI2 c.1681G>T:p.Glu561* and GHRHR c.820_821insC:p.Asp274Alafs*113, and the previously reported variants in GHRHR c.57+1G>A and PROP1 [c.301_302delAG];[c.109+1G>A]. Conclusions Our results indicate that a custom-designed panel is an efficient method to screen simultaneously variants of biological and clinical relevance for congenital GH deficiency. A genetic diagnosis was possible in 5 out of 117 (4%) patients of our cohort. We identified three novel pathogenic variants in GHRHR, OTX2 and GLI2 expanding the spectrum of variants associated with congenital hypopituitarism.

We report four allelic variants (three novel) in three genes previously established as causal for hypopituitarism or related disorders. A novel homozygous variant in the growth hormone gene, GH1 c.171delT (p.Phe 57Leufs*43), was found in a male patient with severe isolated growth hormone deficiency (IGHD) born to consanguineous parents. A hemizygous SOX3 allelic variant (p.Met304Ile) was found in a male patient with IGHD and hypoplastic anterior pituitary. YASARA, a tool to evaluate protein stability, suggests that p.Met304Ile destabilizes the SOX3 protein (ΔΔG = 2.49 kcal/mol). A rare, heterozygous missense variant in the TALE homeobox protein gene, TGIF1 (c.268C&gt, T:p.Arg90Cys) was found in a patient with combined pituitary hormone deficiency (CPHD), diabetes insipidus, and syndromic features of holoprosencephaly (HPE). This variant was previously reported in a patient with severe holoprosencephaly and shown to affect TGIF1 function. A novel heterozygous TGIF1 variant (c.82T&gt, C:p.Ser28Pro) was identified in a patient with CPHD, pituitary aplasia and ectopic posterior lobe. Both TGIF1 variants have an autosomal dominant pattern of inheritance with incomplete penetrance. In conclusion, we have found allelic variants in three genes in hypopituitarism patients. We discuss these variants and associated patient phenotypes in relation to previously reported variants in these genes, expanding our knowledge of the phenotypic spectrum in patient populations.

International audience; Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.

We report four allelic variants (3 novel) in three genes previously established as causal for hypopituitarism or related disorders. A novel homozygous variant in the growth hormone gene, GH1 c.171delT (p. Phe 57Leufs * 43), was found in a male patient with severe isolated growth hormone deficiency (IGHD) born to consanguineous parents. A SOX3 allelic variant (p.Met304Ile) was found in a male patient with IGHD and hypoplastic anterior pituitary. YASARA, a tool to evaluate protein stability, suggests that p.Met304Ile destabilizes the SOX3 protein (ΔΔG = 2.49 kcal/mol). A rare, heterozygous missense variant in the TALE homeobox protein gene, TGIF1 (c.268C>T:p.Arg90Cys) was found in a patient with combined pituitary hormone deficiency (CPHD), diabetes insipidus, and syndromic features of holoprosencephaly (HPE). A novel heterozygous TGIF1 variant (c.82T>C:p.Ser28Pro) was identified in a patient with CPHD, pituitary aplasia and ectopic posterior lobe. Both TGIF1 variants have an autosomal dominant pattern of inheritance with incomplete penetrance. In conclusion, we have found allelic variants in 3 genes in hypopituitarism patients. We discuss these variants and associated patient phenotypes in relation to previously reported variants in these genes, expanding our knowledge of the phenotypic spectrum in patient populations.

Whole Exome Sequencing (WES) has been a useful tool to improve molecular diagnosis in hypopituitarism, leading to the discovery of at least 8 new genes in the last 7 years. However, some genes associated with hypopituitarism show low coverage in this methodology, limiting its use for molecular diagnosis. Our objective is to compare three library prepping kits, NimbleGen (Roche), SureSelect (Agilent) and Nextera (Illumina) examining the best performance related to sequencing quality, exon extension coverage (≥98%) and base depth read (≥20x) of 44 genes associated with hypopituitarism and 32 involved in pituitary development. Three different groups composed of 2 HapMap samples (Group 1), 2 Brazilian patients with hypopituitarism and their respective mothers (Group 2) and 109 random Brazilian samples (Group 3) were sequenced in Illumina platform. Group 1 and 3 were performed using all three library prepping kits, while group 2 was performed with NimbleGen and SureSelect. Although all technologies covered the selected genes with similar efficiency regarding poor (less than 20%) and rich (more than 80%) GC areas, SureSelect has shown to reach the most uniform coverage in the selected region with a lower level of duplicate reads, as well as a higher number of identified pathogenic variants.

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated hypopituitarism patients that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant negative loss of function. Using a high throughput splicing reporter assay, we tested 1,080 single nucleotide variants inPOU1F1. We identified 113 splice disruptive variants, including 23 synonymous variants. We evaluated separate cohorts of hypopituitarism patients and found two different synonymous splice disruptive variants that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in thePOU1F1gene.