Search

NKAP is a ubiquitously expressed nucleoplasmic protein that is currently known as a transcriptional regulatory molecule via its interaction with HDAC3 and spliceosomal proteins. Here, we report a disorder of transcriptional regulation due to missense mutations in the X chromosome gene, NKAP. These mutations are clustered in the C-terminal region of NKAP where NKAP interacts with HDAC3 and post-catalytic spliceosomal complex proteins. Consistent with a role for the C-terminal region of NKAP in embryogenesis, nkap mutant zebrafish with a C-terminally truncated NKAP demonstrate severe developmental defects. The clinical features of affected individuals are highly conserved and include developmental delay, hypotonia, joint contractures, behavioral abnormalities, Marfanoid habitus, and scoliosis. In affected cases, transcriptome analysis revealed the presence of a unique transcriptome signature, which is characterized by the downregulation of long genes with higher exon numbers. These observations indicate the critical role of NKAP in transcriptional regulation and demonstrate that perturbations of the C-terminal region lead to developmental defects in both humans and zebrafish.

International audience; The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and βIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and βIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.

The prenatal finding of a small supernumerary marker chromosome (sSMC) is a challenge for genetic counseling. Our analytic algorithm is based on sSMC frequencies and multicolor FISH to accelerate the procedure. The chromosomal origin, size, and degree of mosaicism of the sSMC then determine the prognosis. We illustrate the effectiveness on 4 prenatally identified de novo mosaic sSMCs derived from chromosomes 13/21, X, 3, and 17. Three sSMC carriers had a good prognosis and apparently healthy children were born, showing no abnormality till the last examination at the age of 4 years. One case had a poor prognosis, and the parents decided to terminate the pregnancy. Our work contributes to the laboratory and clinical management of prenatally detected sSMCs. FISH is a reliable method for fast sSMC evaluation and prognosis assessment; it prevents unnecessary delays and uncertainty, allows informed decision making, and reduces unnecessary pregnancy terminations.

CTG repeat expansions in DMPK cause myotonic dystrophy (DM1) with a continuum of severity and ages of onset. Congenital DM1 (CDM1), the most severe form, presents distinct clinical features, large expansions, and almost exclusive maternal transmission. The correlation between CDM1 and expansion size is not absolute, suggesting contributions of other factors. We determined CpG methylation flanking the CTG repeat in 79 blood samples from 20 CDM1-affected individuals; 21, 27, and 11 individuals with DM1 but not CDM1 (henceforth non-CDM1) with maternal, paternal, and unknown inheritance; and collections of maternally and paternally derived chorionic villus samples (7 CVSs) and human embryonic stem cells (4 hESCs). All but two CDM1-affected individuals showed high levels of methylation upstream and downstream of the repeat, greater than non-CDM1 individuals (p = 7.04958 × 10 −12 ). Most non-CDM1 individuals were devoid of methylation, where one in six showed downstream methylation. Only two non-CDM1 individuals showed upstream methylation, and these were maternally derived childhood onset, suggesting a continuum of methylation with age of onset. Only maternally derived hESCs and CVSs showed upstream methylation. In contrast, paternally derived samples (27 blood samples, 3 CVSs, and 2 hESCs) never showed upstream methylation. CTG tract length did not strictly correlate with CDM1 or methylation. Thus, methylation patterns flanking the CTG repeat are stronger indicators of CDM1 than repeat size. Spermatogonia with upstream methylation may not survive due to methylation-induced reduced expression of the adjacent SIX5 , thereby protecting DM1-affected fathers from having CDM1-affected children. Thus, DMPK methylation may account for the maternal bias for CDM1 transmission, larger maternal CTG expansions, age of onset, and clinical continuum, and may serve as a diagnostic indicator.

Mutations that alter signaling of RAS/MAPK-family proteins give rise to a group of Mendelian diseases known as RASopathies. However, among RASopathies, the matrix of genotype-phenotype relationships is still incomplete, in part because there are many RAS-related proteins and in part because the phenotypic consequences may be variable and/or pleiotropic. Here, we describe a cohort of ten cases, drawn from six clinical sites and over 16,000 sequenced probands, with de novo protein-altering variation in RALA, a RAS-like small GTPase. All probands present with speech and motor delays, and most have intellectual disability, low weight, short stature, and facial dysmorphism. The observed rate of de novo RALA variants in affected probands is significantly higher (p = 4.93 x 10−11) than expected from the estimated random mutation rate. Further, all de novo variants described here affect residues within the GTP/GDP-binding region of RALA; in fact, six alleles arose at only two codons, Val25 and Lys128. The affected residues are highly conserved across both RAL- and RAS-family genes, are devoid of variation in large human population datasets, and several are homologous to positions at which disease-associated variants have been observed in other GTPase genes. We directly assayed GTP hydrolysis and RALA effector-protein binding of the observed variants, and found that all but one tested variant significantly reduced both activities compared to wild-type. The one exception, S157A, reduced GTP hydrolysis but significantly increased RALA-effector binding, an observation similar to that seen for oncogenic RAS variants. These results show the power of data sharing for the interpretation and analysis of rare variation, expand the spectrum of molecular causes of developmental disability to include RALA, and provide additional insight into the pathogenesis of human disease caused by mutations in small GTPases., Author summary While many causes of developmental disabilities have been identified, a large number of affected children cannot be diagnosed despite extensive medical testing. Previously unknown genetic factors are likely to be the culprits in many of these cases. Using DNA sequencing, and by sharing information among many doctors and researchers, we have identified a set of individuals with developmental problems who all have changes to the same gene, RALA. The affected individuals all have similar symptoms, including intellectual disability, speech delay (or no speech), and problems with motor skills like walking. In nearly all of these cases (10 of 11), the genetic change found in the child was not inherited from either parent. The locations and biological properties of these changes suggest that they are likely to disrupt the normal functions of RALA. Functional experiments also show that the genetic changes found in these individuals alter two key functions of RALA. Together, we have provided evidence that genetic changes in RALA can cause developmental disabilities. These results will allow doctors and researchers to identify additional children with the same condition, providing a clinical diagnosis to these families and leading to new research opportunities.

Although de novo missense mutations have been predicted to account for more cases of autism than gene-truncating mutations, most research has focused on the latter. We identified the properties of de novo missense mutations in patients with neurodevelopmental disorders (NDDs) and highlight 35 genes with excess missense mutations. Additionally, 40 amino acid sites were recurrently mutated in 36 genes, and targeted sequencing of 20 sites in 17,688 patients with NDD identified 21 new patients with identical missense mutations. One recurrent site substitution (p.A636T) occurs in a glutamate receptor subunit, GRIA1. This same amino acid substitution in the homologous but distinct mouse glutamate receptor subunit Grid2 is associated with Lurcher ataxia. Phenotypic follow-up in five individuals with GRIA1 mutations shows evidence of specific learning disabilities and autism. Overall, we find significant clustering of de novo mutations in 200 genes, highlighting specific functional domains and synaptic candidate genes important in NDD pathology.

Item does not contain fulltext Verheij syndrome, also called 8q24.3 microdeletion syndrome, is a rare condition characterized by ante- and postnatal growth retardation, microcephaly, vertebral anomalies, joint laxity/dislocation, developmental delay (DD), cardiac and renal defects and dysmorphic features. Recently, PUF60 (Poly-U Binding Splicing Factor 60 kDa), which encodes a component of the spliceosome, has been discussed as the best candidate gene for the Verheij syndrome phenotype, regarding the cardiac and short stature phenotype. To date, only one patient has been reported with a de novo variant in PUF60 that probably affects function (c.505C>T leading to p.(His169Tyr)) associated with DD, microcephaly, craniofacial and cardiac defects. Additional patients were required to confirm the pathogenesis of this association and further delineate the clinical spectrum. Here we report five patients with de novo heterozygous variants in PUF60 identified using whole exome sequencing. Variants included a splice-site variant (c.24+1G>C), a frameshift variant (p.(Ile136Thrfs*31)), two nonsense variants (p.(Arg448*) and p.(Lys301*)) and a missense change (p.(Val483Ala)). All six patients with a PUF60 variant (the five patients of the present study and the unique reported patient) have the same core facial gestalt as 8q24.3 microdeletions patients, associated with DD. Other findings include feeding difficulties (3/6), cardiac defects (5/6), short stature (5/6), joint laxity and/or dislocation (5/6), vertebral anomalies (3/6), bilateral microphthalmia and irido-retinal coloboma (1/6), bilateral optic nerve hypoplasia (2/6), renal anomalies (2/6) and branchial arch defects (2/6). These results confirm that PUF60 is a major driver for the developmental, craniofacial, skeletal and cardiac phenotypes associated with the 8q24.3 microdeletion.

Developmental delay is often a predictor of mental retardation (MR) or autism, two relatively frequent developmental disorders severely affecting intellectual and social functioning. The causes of these conditions remain unknown in most patients. They have a strong genetic component, but the specific genetic defects can only be identified in a fraction of patients. Recent developments in genomics supported the establishment of the causal link between copy number variants in the genomes of some patients and their affection. One of the techniques suitable for this analysis is array comparative genome hybridization, which can be used both for detailed mapping of chromosome rearrangements identified by classical cytogenetics and for the identification of novel submicroscopic gains or losses of genetic material. We illustrate the power of this approach in two patients. Patient 1 had a cytogenetically visible deletion of chromosome X and the molecular analysis was used to specify the gene content of the deletion and the prognosis of the child. Patient 2 had a seemingly normal karyotype and the analysis revealed a small recurrent deletion of chromosome 1 likely to be responsible for his phenotype. However, the genetic dissection of MR and autism is complicated by high heterogeneity of the genetic aberrations among patients and by broad variability of phenotypic effects of individual genetic defects.

The breakpoint junction on a ring chromosome 17 in a girl with autism, mental retardation, mild dysmorphism and neurofibromatosis was identified and analysed at the nucleotide level. The extent of the deleted segments was about 1.9 Mb on 17p and about 1.0 Mb on 17q. The structure of the junction between the 17p and 17q arms, especially the lack of significant homology between the juxtaposed genomic regions and the presence of short microhomology at the junction site, indicated non-homologous end joining as the most likely mechanism leading to the rearrangement. In addition to the 17p-17q junction itself, a de novo 1 kb deletion in a distance of 400 bp from the junction was identified, which arose most likely as a part of the rearrangement. The defect directly inactivated 3 genes, and the deleted terminal chromosome segments harboured 27 and 14 protein-coding genes from 17p and 17q, respectively. Several of the genes affected by the rearrangement are candidates for the symptoms observed in the patient. Additional rearrangements similar to the 1 kb deletion observed in our patient may remain undetected but can participate in the phenotype of patients with chromosomal aberrations. They can also be the reason for repeated failures to clone breakpoint junctions in other patients described in the literature.

BACKGROUND. A decrease in the age at cancer onset and increase in cancer incidence in successive generations in Li-Fraumeni syndrome (LFS) families with germline TP53 mutations have been previously described. In the current study a possible relation was analyzed between telomere length and cancer onset in TP53 mutation carriers. METHODS. Telomere length was measured using real-time quantitative polymerase chain reaction (PCR) in 20 carriers of germline TP53 mutations and in 83 unrelated healthy individuals. According to the age at blood sampling, patients and controls were divided into 2 age groups, children and adults. Telomere length was correlated to TP53 mutation status and telomere shortening in patients to the age at cancer onset. A t-test and linear regression were used to analyze the data. RESULTS. Compared with healthy controls, telomere length was significantly shorter both in the child (P = .001) and adult (P = .034) germline T53 mutation carriers. Although a statistically significant correlation between telomere shortening and the age at cancer onset was not observed, there was a trend of shorter telomeres in mutation carriers affected in childhood compared with those affected later in life. Neither cancer therapy nor sex differences were likely to affect the results. CONCLUSIONS. The findings suggest a possible link between the carriership of a germline TP53 mutation, telomere length, predisposition to early-onset cancer, and anticipation in LFS. Cancer 2007. © 2007 American Cancer Society.

A transition from fetal hemoglobin (HbF) to adult hemoglobin (HbA) normally occurs within a few months after birth. Increased production of HbF after this period of infancy ameliorates clinical symptoms of the major disorders of adult β-hemoglobin: β-thalassemia and sickle cell disease. The transcription factor BCL11A silences HbF and has been an attractive therapeutic target for increasing HbF levels; however, it is not clear to what extent BCL11A inhibits HbF production or mediates other developmental functions in humans. Here, we identified and characterized 3 patients with rare microdeletions of 2p15-p16.1 who presented with an autism spectrum disorder and developmental delay. Moreover, these patients all exhibited substantial persistence of HbF but otherwise retained apparently normal hematologic and immunologic function. Of the genes within 2p15-p16.1, only BCL11A was commonly deleted in all of the patients. Evaluation of gene expression data sets from developing and adult human brains revealed that BCL11A expression patterns are similar to other genes associated with neurodevelopmental disorders. Additionally, common SNPs within the second intron of BCL11A are strongly associated with schizophrenia. Together, the study of these rare patients and orthogonal genetic data demonstrates that BCL11A plays a central role in silencing HbF in humans and implicates BCL11A as an important factor for neurodevelopment.

Genitopatellar syndrome (GPS) and Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) are two distinct clinically overlapping syndromes caused by de novo heterozygous truncating mutations in the KAT6B gene encoding lysine acetyltransferase 6B, a part of the histone H3 acetyltransferase complex. We describe an 8-year-old girl with a KAT6B mutation and a combined GPS/SBBYSS phenotype. The comparison of this patient with 61 previously published cases with KAT6B mutations and GPS, SBBYSS or combined GPS/SBBYSS phenotypes allowed us to separate the KAT6B mutations into four groups according to their position in the gene (reflecting nonsense mediated RNA decay and protein domains) and their clinical outcome. We suggest that mutations in mid-exon 18 corresponding to the C-terminal end of the acidic (Asp/Glu-rich) domain of KAT6B may have more variable expressivity leading to GPS, SBBYSS or combined phenotypes, in contrast to defects in other regions of the gene which contribute more specifically to either GPS or SBBYSS. Notwithstanding the clinical overlap, our cluster analysis of phenotypes of all known patients with KAT6B mutations supports the existence of two clinical entities, GPS and SBBYSS, as poles within the KAT6B-related disease spectrum. The awareness of these phenomena is important for qualified genetic counselling of patients with KAT6B mutations.

Both gain- and loss-of-function mutations have recently implicated HCFC1 in neurodevelopmental disorders. Here, we extend our previous HCFC1 over-expression studies by employing short hairpin RNA to reduce the expression of Hcfc1 in embryonic neural cells. We show that in contrast to over-expression, loss of Hcfc1 favoured proliferation of neural progenitor cells at the expense of differentiation and promoted axonal growth of post-mitotic neurons. To further support the involvement of HCFC1 in neurological disorders, we report two novel HCFC1 missense variants found in individuals with intellectual disability (ID). One of these variants, together with three previously reported HCFC1 missense variants of unknown pathogenicity, were functionally assessed using multiple cell-based assays. We show that three out of the four variants tested result in a partial loss of HCFC1 function. While over-expression of the wild-type HCFC1 caused reduction in HEK293T cell proliferation and axonal growth of neurons, these effects were alleviated upon over-expression of three of the four HCFC1 variants tested. One of these partial loss-of-function variants disrupted a nuclear localization sequence and the resulting protein displayed reduced ability to localize to the cell nucleus. The other two variants displayed negative effects on the expression of the HCFC1 target gene MMACHC, which is responsible for the metabolism of cobalamin, suggesting that these individuals may also be susceptible to cobalamin deficiency. Together, our work identifies plausible cellular consequences of missense HCFC1 variants and identifies likely and relevant disease mechanisms that converge on embryonic stages of brain development.

International audience; Although most retroposons that arose by reverse transcription of cellular mRNAs and by reintegration into the genome are nonfunctional, several examples exist in which the retroposon acquired a novel function and became fixed in the genome as a functional gene. We identified another such case: the ubiquitously expressed X-linked XAP-5 gene with unknown function gave rise to its retroposed counterpart, XAP-5-like (X5L), which has an intronless open reading frame and is autosomal in human. Phylogenetic analysis of the human and mouse XAP-5 and X5L genes shows that the retroposition most likely took place before the radiation of eutherian mammals. The XAP-5 and X5L genes are expressed in a wide range of tissues but are differentially expressed in testis. The ancient origin and broad expression of the X5L retroposon indicate that the XAP-5 and X5L genes may have assumed different functions in somatic cells. In addition to this, because of its autosomal location and its high level and particular pattern of expression in spermatogenic cells, the X5L expression in testis may compensate for the X-linked XAP-5 gene, which may be silenced during spermatogenesis.

Microdeletions spanning 2p14-p15 have recently been described in two patients with developmental and speech delay and intellectual disability but no congenital malformations or severe facial dysmorphism. We report a 4-year-old boy with a de novo 3.7 Mb long deletion encompassing the region deleted in the previous cases. The patient had clinical features partly consistent with the published cases including intellectual disability, absent speech, microcephaly, long face, bulbous nasal tip and thin upper lip, but his overall clinical picture was more severe compared to the published patients. The identification of this additional patient and a detailed analysis of deletions identified in various patient cohorts and in normal individuals support the existence of a new rare microdeletion syndrome in 2p14-p15. Its critical region is in the vicinity of but clearly separate from the minimal region deleted in the well established 2p15-p16.1 microdeletion syndrome. A thorough comparison of the deletions and phenotypes indicates that multiple genes located in this region may be involved in intellectual functioning, and that some patients may show composite and more complex phenotypes due to deletions spanning both critical regions.

The Huntington's disease (HD) gene has been mapped in 4p16.3 but has eluded identification. We have used haplotype analysis of linkage disequilibrium to spotlight a small segment of 4p16.3 as the likely location of the defect. A new gene, 1715, isolated using cloned trapped exons from the target area contains a polymorphic trinucleotide repeat that is expanded and unstable on HD chromosomes. A (CAG)n repeat longer than the normal range was observed on HD chromosomes from all 75 disease families examined, comprising a variety of ethnic backgrounds and 4p 16.3 haplotypes. The (CAG)n repeat appears to be located within the coding sequence of a predicted ≈348 kd protein that is widely expressed but unrelated to any known gene. Thus, the HD mutation involves an unstable DNA segment, similar to those described in fragile X syndrome, spino-bulbar muscular atrophy, and myotonic dystrophy, acting in the context of a novel 4p16.3 gene to produce a dominant phenotype.

An essential requirement in the analysis of genomes is the identification of functionally important sequence elements, which are often evolutionarily conserved. We describe here the development of a novel procedure for the selective isolation of conserved sequences which is based on hybridization of PCR-amplifiable DNA fragments from the whole genome of one species to biotinylated DNA from a genomic region of another species. The interspecies DNA hybrids are immobilized and the PCR-amplifiable DNA fragments are eluted, amplified and after further hybridization-amplification rounds cloned. This method was used for the generation of sublibraries of conserved sequences from mouse and pig DNA from regions corresponding to cosmids from the human Xq28 region. Mouse and pig homologs of sequences containing exons of known human genes, as well as exons from novel genes have been identified.

A telomere YAC clone containing the most distal 115 kb of chromosome arm 4p has been previously isolated. This clone is of particular interest as it spans a potential candidate region for the Huntington disease gene. The YAC was subcloned into a phage vector, and a high-resolution restriction map extending to within 13 kb of the telomere was constructed. In situ hybridization of the YAC to human metaphase spreads gives a peak of hybridization on 4pter but also an increase in the number of signals close to several other telomeres. Where possible, these results were investigated further by the hybridization of probes from the YAC to somatic cell hybrids containing single human chromosomes. This analysis indicates that the most telomeric 60 kb of chromosome arm 4p is homologous to telomeric regions on 13p, 15p, 21p, and 22p. The extent of this homology makes it less likely that the mutation for Huntington's disease is located within the telomere YAC clone.

The gene for Huntington disease, a neurodegenerative disorder with autosomal dominant inheritance, has been localized to the terminal portion of the short arm of human chromosome 4 (4p16.3) by linkage analysis. Since eventual isolation of the gene requires the application of high-resolution genetic analysis coupled with long-range DNA mapping and cloning techniques, we have constructed a physical map of the chromosomal region 4p16.3 using more than 20 independently derived probes. We have grouped these markers into three clusters which have been ordered and oriented by genetic and somatic cell genetic mapping information. The mapped region extends from D4S10 (G8) toward the telomere and covers minimally 5 Mb.

We describe a girl with neurofibromatosis type 1 (NF1), mild dysmorphic features, growth and mental retardation, autism, and mosaicism of ring chromosome 17 and chromosome 17 monosomy. The extent of genetic material deleted from the ring chromosome was determined using a combination of classical cytogenetics, fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) to be 0.6-2.5 Mb on 17p, and up to about 10 Mb on 17q. Based on our observations and on a review of the literature we argue that in addition to a universal "ring syndrome" which is based on ring instability and is less specific for the chromosome involved, various ring chromosomes underlie their own characteristic phenotypes. We propose that the symptoms leading to the diagnosis of NF1 in our patient could be attributed to mosaic hemizygosity for the NF1 gene in some of her somatic cells. A similar mechanism or a direct involvement of respective disease genes in the aberration could possibly influence also the development of autism and other symptoms. We raise a question if the loss of one copy of chromosome 17 from a substantial fraction of somatic cells can have specific consequences also for future risks of the patient, for example, due to the mosaic hemizygosity for the BRCA1 and TP53 genes.

Anticipation in the age at onset of cancer in successive generations was described in several familial cancer syndromes. Based on multiple statistical analyses of a database of families with germline TP53 mutations, and using several different approaches and measures to eliminate possible biases, we show that anticipation may be a feature of the Li-Fraumeni syndrome. Definitive proof of anticipation in pedigrees with germline TP53 mutations will require more family data and further analysis, as well as research on the role of the p53 protein in processes like genome stability, which may represent the biological basis of anticipation in these families. This should have important practical implications for genetic testing, counselling, and preventative care for individuals at risk.

Background Inversions are balanced structural chromosome rearrangements, which can influence gene expression and the risk of unbalanced chromosome constitution in offspring. Many examples of inversion polymorphisms exist in human, affecting both heterochromatic regions and euchromatin. Results We describe a novel, 15 Mb long paracentric inversion, inv(21)(q21.1q22.11), affecting more than a third of human 21q. Despite of its length, the inversion cannot be detected using karyotyping due to similar band patterns on the normal and inverted chromosomes, and is therefore likely to escape attention. Its identification was aided by the repeated observation of the same pair of 150 kb long duplications present in cis on chromosome 21 in three Czech families subjected to microarray analysis. The finding prompted us to hypothesise that this co-occurrence of two remote duplications could be associated with an inversion of the intervening segment, and this speculation turned out to be right. The inversion was confirmed in a series of FISH experiments which also showed that the second copy of each of the duplications was always located at the opposite end of the inversion. The presence of the same pair of duplications in additional individuals reported in public databases indicates that the inversion may also be present in other populations. Three out of the total of about 4000 chromosomes 21 examined in our sample carried the duplications and were inverted, corresponding to carrier frequency of about 1/660. Although the breakpoints affect protein-coding genes, the occurrence of the inversion in normal parents and siblings of our patients and the occurrence of the duplications in unaffected controls in databases indicate that this rare variant is rather non-pathogenic. The inverted segment carried an identical shared haplotype in the three families studied. The haplotypes, however, diverged very rapidly in the flanking regions, possibly pointing to an ancient founder event at the origin of the inversion. Conclusions The identification of inv(21)(q21.1q22.11) supports the notion that paracentric inversions are the most common form of chromosomal variation and that some of them may still remain undetected.

A systematic search for expressed sequences in the human Xq28 region resulted in the isolation of 8.5 kb large contigs of human and murine cDNAs with no apparent conserved open reading frames. These cDNAs were found to be derived from the 3"-untranslated region (3"-UTR) of the methyl-CpG-binding protein 2 gene ( MeCP2 ). This long 3"-UTR is part of an alternatively polyadenylated, 10.1 kb MeCP2 transcript which is differentially expressed in human brain and other tissues. RNA in situ hybridization to sections of mouse embryo and adult tissues of an Mecp2 3"-UTR probe showed ubiquitous low level expression in early organogenesis and enhanced expression in the hippocampus during formation of the differentiated brain. Sequence comparison between the human and mouse homologues revealed several blocks of very high conservation separated by less conserved sequences. Additional support for a domain-like conservation pattern of the long 3"-UTR of the MeCP2 gene was obtained by examining conservation in the chimpanzee, orangutan, macaque, hamster, rat and kangaroo. The minimum free energy distribution for the predicted RNA secondary structure was very similar in human and mouse sequences. In particular, the conserved blocks were predicted to be of high minimum free energy, which suggests weak secondary structure with respect to RNA folding. The fact that both the sequence and predicted secondary structure have been highly conserved during evolution suggests that both the primary sequence and the three-dimensional structure of the 3"-UTR may be important for its function in post-transcriptional regulation of MeCP2 expression.

International audience; BACKGROUND: Microdeletions of 14q22q23 have been associated with eye abnormalities and pituitary defects. Other phenotypic features in deletion carriers including hearing loss and response to growth hormone therapy are less well recognized. We studied genotype and phenotype of three newly identified children with 14q22q23 deletions, two girls and one boy with bilateral anophthalmia, and compared them with previously published deletion patients and individuals with intragenic defects in genes residing in the region. RESULTS: The three deletions were de novo and ranged in size between 5.8 and 8.9 Mb. All three children lacked one copy of the OTX2 gene and in one of them the deletion involved also the BMP4 gene. All three patients presented partial conductive hearing loss which tended to improve with age. Analysis of endocrine and growth phenotypes showed undetectable anterior pituitary, growth hormone deficiency and progressive growth retardation in all three patients. Growth hormone therapy led to partial catch-up growth in two of the three patients but just prevented further height loss in the third. CONCLUSIONS: The pituitary hypoplasia, growth hormone deficiency and growth retardation associated with 14q22q23 microdeletions are very remarkable, and the latter appears to have an atypical response to growth hormone therapy in some of the cases.