Simpson-Golabi-Behmel syndrome type 1 in a 27-week macrosomic preterm newborn: the diagnostic value of rib malformations and index nail and finger hypoplasia.

The Simpson-Golabi-Behmel syndrome type 1 (SGBS1, OMIM #312870) is an X-linked overgrowth condition comprising abnormal facial appearance, supernumerary nipples, congenital heart defects, polydactyly, fingernail hypoplasia, increased risk of neonatal death and of neoplasia. It is caused by mutation/deletion of the GPC3 gene. We describe a macrosomic 27-week preterm newborn with SGBS1 who presents a novel GPC3 mutation and emphasize the phenotypic aspects which allow a correct diagnosis neonatally in particular the rib malformations, hypoplasia of index finger and of the same fingernail, and 2nd-3rd finger syndactyly.

Biological activity of ectodysplasin A is conditioned by its collagen and heparan sulfate proteoglycan-binding domains.

Mutations in the TNF family ligand EDA1 cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition characterized by defective development of skin appendages. The EDA1 protein displays a proteolytic processing site responsible for its conversion to a soluble form, a collagen domain, and a trimeric TNF homology domain (THD) that binds the receptor EDAR. In-frame deletions in the collagen domain reduced the thermal stability of EDA1. Removal of the collagen domain decreased its activity about 100-fold, as measured with natural and engineered EDA1-responsive cell lines. The collagen domain could be functionally replaced by multimerization domains or by cross-linking antibodies, suggesting that it functions as an oligomerization unit. Surprisingly, mature soluble EDA1 containing the collagen domain was poorly active when administered in newborn, EDA-deficient (Tabby) mice. This was due to a short stretch of basic amino acids located at the N terminus of the collagen domain that confers EDA1 with proteoglycan binding ability. In contrast to wild-type EDA1, EDA1 with mutations in this basic sequence was a potent inducer of tail hair development in vivo. Thus, the collagen domain activates EDA1 by multimerization, whereas the proteoglycan-binding domain may restrict the distribution of endogeneous EDA1 in vivo.

BCOR analysis in patients with OFCD and Lenz microphthalmia syndromes, mental retardation with ocular anomalies, and cardiac laterality defects.

Oculofaciocardiodental (OFCD) and Lenz microphthalmia syndromes form part of a spectrum of X-linked microphthalmia disorders characterized by ocular, dental, cardiac and skeletal anomalies and mental retardation. The two syndromes are allelic, caused by mutations in the BCL-6 corepressor gene (BCOR). To extend the series of phenotypes associated with pathogenic mutations in BCOR, we sequenced the BCOR gene in patients with (1) OFCD syndrome, (2) putative X-linked ('Lenz') microphthalmia syndrome, (3) isolated ocular defects and (4) laterality phenotypes. We present a new cohort of females with OFCD syndrome and null mutations in BCOR, supporting the hypothesis that BCOR is the sole molecular cause of this syndrome. We identify for the first time mosaic BCOR mutations in two females with OFCD syndrome and one apparently asymptomatic female. We present a female diagnosed with isolated ocular defects and identify minor features of OFCD syndrome, suggesting that OFCD syndrome may be mild and underdiagnosed. We have sequenced a cohort of males diagnosed with putative X-linked microphthalmia and found a mutation, p.P85L, in a single case, suggesting that BCOR mutations are not a major cause of X-linked microphthalmia in males. The absence of BCOR mutations in a panel of patients with non-specific laterality defects suggests that mutations in BCOR are not a major cause of isolated heart and laterality defects. Phenotypic analysis of OFCD and Lenz microphthalmia syndromes shows that in addition to the standard diagnostic criteria of congenital cataract, microphthalmia and radiculomegaly, patients should be examined for skeletal defects, particularly radioulnar synostosis, and cardiac/laterality defects.

Additional data for nuclear DNA give new insights into the phylogenetic position of Sorex granarius within the Sorex araneus group.

Many species contain genetic lineages that are phylogenetically intermixed with those of other species. In the Sorex araneus group, previous results based on mtDNA and Y chromosome sequence data showed an incongruent position of Sorex granarius within this group. In this study, we explored the relationship between species within the S. araneus group, aiming to resolve the particular position of S. granarius. In this context, we sequenced a total of 2447 base pairs (bp) of X-linked and nuclear genes from 47 individuals of the S. araneus group. The same taxa were also analyzed within a Bayesian framework with nine autosomal microsatellites. These analyses revealed that all markers apart from mtDNA showed similar patterns, suggesting that the problematic position of S. granarius is best explained by an incongruent behavior by mtDNA. Given their close phylogenetic relationship and their close geographic distribution, the most likely explanation for this pattern is past mtDNA introgression from S. araneus race Carlit to S. granarius.

Understanding mutational and selective processes that govern gene duplication in mammals

Abstract : Gene duplication is an essential source of material for the origin of genetic novelties. The reverse transcription of source gene mRNA followed by the genomic insertion of the resulting cDNA - retroposition - has provided the human genome with at least ~3600 detectable retrocopies. We find that ~30% of these retrocopies are transcribed, generally in testes. Their transcription often relies on preexisting regulatory elements (or open chromatin) close to their insertion site, which is illustrated by mRNA molecules containing retrocopies fused to their neighboring genes. Retrocopies appear to have been profoundly shaped by selection. Consistently, human retrocopies with an intact open reading (ORF) are more often transcribed than retropseudogenes, which leads to a minimal estimate of 120 functional retrogenes present in our genome. We also performed an analysis of Ka/Ks for human retrocopies. This analysis demonstrates that several intact retrocopies evolved under purifying selection and yields an estimated formation rate of ~1 retrogene per million year in the primate lineage. Using DNA sequencing and evolutionary simulations, we have identified 7 such primate-specific retrogenes that emerged on the lineage leading to humans In therian genomes, we found an excess of retrogenes with X-linked parents. Expression analyses support the idea that this "out of X" movement was driven by natural selection to produce autosomal functional counterparts for X-linked genes, which are silenced during male meiosis. Phylogenetic dating of this "out of X" movement suggests that our sex chromosomes arose about 180 MYA ago and are thus much younger than previously thought. Finally, we have also analyzed young gene duplications (and deletions) that arose by non allelic-homologous recombination and are not fixed in species. Using wild-caught and laboratory animals, we detected thousands of DNA segments that are polymorphic in copy number in mice. These copy number variants were found to profoundly alter the transcriptome of several mouse tissues. Strikingly, their influence on gene expression is not limited to the gene they contain but seems to extend to genes located up to 1.5 million bases away.

The TREAT-NMD Duchenne Muscular Dystrophy Registries: Conception, Design, and Utilization by Industry and Academia.

Duchenne muscular dystrophy (DMD) is an X-linked genetic disease, caused by the absence of the dystrophin protein. Although many novel therapies are under development for DMD, there is currently no cure and affected individuals are often confined to a wheelchair by their teens and die in their twenties/thirties. DMD is a rare disease (prevalence <5/10,000). Even the largest countries do not have enough affected patients to rigorously assess novel therapies, unravel genetic complexities, and determine patient outcomes. TREAT-NMD is a worldwide network for neuromuscular diseases that provides an infrastructure to support the delivery of promising new therapies for patients. The harmonized implementation of national and ultimately global patient registries has been central to the success of TREAT-NMD. For the DMD registries within TREAT-NMD, individual countries have chosen to collect patient information in the form of standardized patient registries to increase the overall patient population on which clinical outcomes and new technologies can be assessed. The registries comprise more than 13,500 patients from 31 different countries. Here, we describe how the TREAT-NMD national patient registries for DMD were established. We look at their continued growth and assess how successful they have been at fostering collaboration between academia, patient organizations, and industry.

Cardiac and vascular hypertrophy in Fabry disease: evidence for a new mechanism independent of blood pressure and glycosphingolipid deposition.

OBJECTIVE: Fabry disease is an X-linked disorder resulting from alpha-galactosidase A deficiency. The cardiovascular findings include left ventricular hypertrophy (LVH) and increased intima-media thickness of the common carotid artery (CCA IMT). The current study examined the possible correlation between these parameters. To corroborate these clinical findings in vitro, plasma from Fabry patients was tested for possible proliferative effect on rat vascular smooth muscle cells (vascular smooth muscle cell [VSMC]) and mouse neonatal cardiomyocytes. METHODS AND RESULTS: Thirty male and 38 female patients were enrolled. LVH was found in 60% of men and 39% of women. Increased CCA IMT was equally present in males and females. There was a strong positive correlation between LV mass and CCA IMT (r2=0.27; P<0.0001). VSMC and neonatal cardiomyocyte proliferative response in vitro correlated with CCA IMT (r2=0.39; P<0.0004) and LV mass index (r2=0.19; P=0.028), respectively. CONCLUSIONS: LVH and CCA IMT occur concomitantly in Fabry suggesting common pathogenesis. The underlying cause may be a circulating growth-promoting factor whose presence has been confirmed in vitro.

Roles of transient guidepost neurons in corpus callosum formation and guidance

RESUMENeurones transitoires jouant un rôle de cibles intermédiaires dans le guidage des axones du corps calleuxLe guidage axonal est une étape clé permettant aux neurones d'établir des connexions synaptiques et de s'intégrer dans un réseau neural fonctionnel de manière spécifique. Des cellules-cibles intermédiaires appelées « guidepost » aident les axones à parcourir de longues distances dans le cerveau en leur fournissant des informations directionnelles tout au long de leur trajet. Il a été démontré que des sous-populations de cellules gliales au niveau de la ligne médiane guident les axones du corps calleux (CC) d'un hémisphère vers l'autre. Bien qu'il fût observé que le CC en développement contenait aussi des neurones, leur rôle était resté jusqu'alors inconnu.La publication de nos résultats a montré que pendant le développement embryonnaire, le CC contient des glies mais aussi un nombre considérable de neurones glutamatergiques et GABAergiques, nécessaires à la formation du corps calleux (Niquille et al., PLoS Biology, 2009). Dans ce travail, j'ai utilisé des techniques de morphologie et d'imagerie confocale 3D pour définir le cadre neuro-anatomique de notre modèle. De plus, à l'aide de transplantations sur tranches in vitro, de co-explants, d'expression de siRNA dans des cultures de neurones primaires et d'analyse in vivo sur des souris knock-out, nous avons démontré que les neurones du CC guident les axones callosaux en partie grâce à l'action attractive du facteur de guidage Sema3C sur son récepteur Npn- 1.Récemment, nous avons étudié l'origine, les aspects dynamiques de ces processus, ainsi que les mécanismes moléculaires impliqués dans la mise en place de ce faisceau axonal (Niquille et al., soumis). Tout d'abord, nous avons précisé l'origine et l'identité des neurones guidepost GABAergiques du CC par une étude approfondie de traçage génétique in vivo. J'ai identifié, dans le CC, deux populations distinctes de neurones GABAergiques venant des éminences ganglionnaires médiane (MGE) et caudale (CGE). J'ai ensuite étudié plus en détail les interactions dynamiques entre neurones et axones du corps calleux par microscopie confocale en temps réel. Puis nous avons défini le rôle de chaque sous-population neuronale dans le guidage des axones callosaux et de manière intéressante les neurones GABAergic dérivés de la MGE comme ceux de la CGE se sont révélés avoir une action attractive pour les axones callosaux dans des expériences de transplantation. Enfin, nous avons clarifié la base moléculaire de ces mécanismes de guidage par FACS sorting associé à un large criblage génétique de molécules d'intérêt par une technique très sensible de RT-PCR et ensuite ces résultats ont été validés par hybridation in situ.Nous avons également étudié si les neurones guidepost du CC étaient impliqués dans son agénésie (absence de CC), présente dans nombreux syndromes congénitaux chez 1 humain. Le gène homéotique Aristaless (Arx) contrôle la migration des neurones GABAergiques et sa mutation conduit à de nombreuses pathologies humaines, notamment la lissencéphalie liée à IX avec organes génitaux anormaux (XLAG) et agénésie du CC. Fait intéressant, nous avons constaté qu'ARX est exprimé dans toutes les populations GABAergiques guidepost du CC et que les embryons mutant pour Arx présentent une perte drastique de ces neurones accompagnée de défauts de navigation des axones (Niquille et al., en préparation). En outre, nous avons découvert que les souris déficientes pour le facteur de transcription ciliogenic RFX3 souffrent d'une agénésie du CC associé avec des défauts de mise en place de la ligne médiane et une désorganisation secondaire des neurones glutamatergiques guidepost (Benadiba et al., submitted). Ceci suggère fortement l'implication potentielle des deux types de neurones guidepost dans l'agénésie du CC chez l'humain.Ainsi, mon travail de thèse révèle de nouvelles fonctions pour ces neurones transitoires dans le guidage axonal et apporte de nouvelles perspectives sur les rôles respectifs des cellules neuronales et gliales dans ce processus.ABSTRACTRole of transient guidepost neurons in corpus callosum development and guidanceAxonal guidance is a key step that allows neurons to build specific synaptic connections and to specifically integrate in a functional neural network. Intermediate targets or guidepost cells act as critical elements that help to guide axons through long distance in the brain and provide information all along their travel. Subpopulations of midline glial cells have been shown to guide corpus callosum (CC) axons to the contralateral cerebral hemisphere. While neuronal cells are also present in the developing corpus callosum, their role still remains elusive.Our published results unravelled that, during embryonic development, the CC is populated in addition to astroglia by numerous glutamatergic and GABAergic guidepost neurons that are essential for the correct midline crossing of callosal axons (Niquille et al., PLoS Biology, 2009). In this work, I have combined morphological and 3D confocal imaging techniques to define the neuro- anatomical frame of our system. Moreover, with the use of in vitro transplantations in slices, co- explant experiments, siRNA manipulations on primary neuronal culture and in vivo analysis of knock-out mice we have been able to demonstrate that CC neurons direct callosal axon outgrowth, in part through the attractive action of Sema3C on its Npn-1 receptor.Recently, we have studied the origin, the dynamic aspects of these processes as well as the molecular mechanisms involved in the establishment of this axonal tract (Niquille et al., submitted). First, we have clarified the origin and the identity of the CC GABAergic guidepost neurons using extensive in vivo cell fate-mapping experiments. We identified two distinct GABAergic neuronal subpopulations, originating from the medial (MGE) and caudal (CGE) ganglionic eminences. I then studied in more details the dynamic interactions between CC neurons and callosal axons by confocal time-lapse video microscopy and I have also further characterized the role of each guidepost neuronal subpopulation in callosal guidance. Interestingly, MGE- and CGE-derived GABAergic neurons are both attractive for callosal axons in transplantation experiments. Finally, we have dissected the molecular basis of these guidance mechanisms by using FACS sorting combined with an extensive genetic screen for molecules of interest by a sensitive RT-PCR technique, as well as, in situ hybridization.I have also investigated whether CC guidepost neurons are involved in agenesis of the CC which occurs in numerous human congenital syndromes. Aristaless-related homeobox gene (Arx) regulates GABAergic neuron migration and its mutation leads to numerous human pathologies including X-linked lissencephaly with abnormal genitalia (XLAG) and severe CC agenesis. Interestingly, I found that ARX is expressed in all the guidepost GABAergic neuronal populations of the CC and that Arx-/- embryos exhibit a drastic loss of CC GABAergic interneurons accompanied by callosal axon navigation defects (Niquille et al, in preparation). In addition, we discovered that mice deficient for the ciliogenic transcription factor RFX3 suffer from CC agenesis associated with early midline patterning defects and a secondary disorganisation of guidepost glutamatergic neurons (Benadiba et al., submitted). This strongly points out the potential implication of both types of guidepost neurons in human CC agenesis.Taken together, my thesis work reveals novel functions for transient neurons in axonal guidance and brings new perspectives on the respective roles of neuronal and glial cells in these processes.

Normal variation in fronto-occipital circuitry and cerebellar structure with an autism-associated polymorphism of CNTNAP2.

Recent genetic studies have implicated a number of candidate genes in the pathogenesis of Autism Spectrum Disorder (ASD). Polymorphisms of CNTNAP2 (contactin-associated like protein-2), a member of the neurexin family, have already been implicated as a susceptibility gene for autism by at least 3 separate studies. We investigated variation in white and grey matter morphology using structural MRI and diffusion tensor imaging. We compared volumetric differences in white and grey matter and fractional anisotropy values in control subjects characterised by genotype at rs7794745, a single nucleotide polymorphism in CNTNAP2. Homozygotes for the risk allele showed significant reductions in grey and white matter volume and fractional anisotropy in several regions that have already been implicated in ASD, including the cerebellum, fusiform gyrus, occipital and frontal cortices. Male homozygotes for the risk alleles showed greater reductions in grey matter in the right frontal pole and in FA in the right rostral fronto-occipital fasciculus compared to their female counterparts who showed greater reductions in FA of the anterior thalamic radiation. Thus a risk allele for autism results in significant cerebral morphological variation, despite the absence of overt symptoms or behavioural abnormalities. The results are consistent with accumulating evidence of CNTNAP2's function in neuronal development. The finding suggests the possibility that the heterogeneous manifestations of ASD can be aetiologically characterised into distinct subtypes through genetic-morphological analysis.

Aarskog-Scott syndrome: clinical update and report of nine novel mutations of the FGD1 gene.

Mutations in the FGD1 gene have been shown to cause Aarskog-Scott syndrome (AAS), or facio-digito-genital dysplasia (OMIM#305400), an X-linked disorder characterized by distinctive genital and skeletal developmental abnormalities with a broad spectrum of clinical phenotypes. To date, 20 distinct mutations have been reported, but little phenotypic data are available on patients with molecularly confirmed AAS. In the present study, we report on our experience of screening for mutations in the FGD1 gene in a cohort of 60 European patients with a clinically suspected diagnosis of AAS. We identified nine novel mutations in 11 patients (detection rate of 18.33%), including three missense mutations (p.R402Q; p.S558W; p.K748E), four truncating mutations (p.Y530X; p.R656X; c.806delC; c.1620delC), one in-frame deletion (c.2020_2022delGAG) and the first reported splice site mutation (c.1935+3A>C). A recurrent mutation (p.R656X) was detected in three independent families. We did not find any evidence for phenotype-genotype correlations between type and position of mutations and clinical features. In addition to the well-established phenotypic features of AAS, other clinical features are also reported and discussed.

Lack of MRI neurohypophyseal bright signal in a child with congenital nephrogenic diabetes insipidus

Congenital nephrogenic diabetes insipidus (CNDI) is a rare disease characterized by the inability of the kidney to respond to arginine vasopressin (AVP). The absence of the neurohypophyseal 'bright signal' on T1 sequence magnetic resonance imaging (MRI) is considered as an argument in favour of the diagnosis of central diabetes insipidus (CDI). This observation is challenged as we hereby present a case of a child diagnosed with CNDI and who did not present MRI pituitary bright signal. A 6-month-old male presented with failure to thrive, polyuria and polydypsia. Family history revealed that the mother, 35 years of age, had been presenting polydypsia and polyuria, and she was investigated at the age of 6 years with no concluding diagnosis. The patient's physical exam showed a weight of 5215 g (−3 DS) and clinical signs of dehydration. The patient's plasma sodium level was 155 mmol/L, osmolality 305 mOsm/kg and urine osmolality 150 mOsm/kg. Brain MRI showed in T1 sequences the absence of the posterior pituitary bright signal suggesting the diagnosis of CDI (Figure 1). The child was treated with synthetic AVP analogue 1-desamino-8-d-arginine vasopressin (DDAVP) without improvement, which led to the consideration of CNDI. The diagnosis was confirmed by an elevated serum level of AVP of 214 pmol/L (reference value ≤4.34 pmol/L) and by genetic analysis demonstrating and T106C mutation in the V2R (X-linked CNDI). The child was treated with thiazide diuretic and increased fluids with restricted sodium intake. This resulted in catch-up growth and improved neurological development. A follow-up MRI was performed 6 months after the start of therapy with the same technique. At that time, the child's weight had improved to 9310 g (−1.5 DS) corresponding to a gain of 22 g per day, and he did not present any clinical signs of dehydration and had a normal plasma level of sodium (140 mmol/L). MRI showed that the bright signal was still absent.

Evolutionary fate of retroposed gene copies in the human genome.

Given that retroposed copies of genes are presumed to lack the regulatory elements required for their expression, retroposition has long been considered a mechanism without functional relevance. However, through an in silico assay for transcriptional activity, we identify here >1,000 transcribed retrocopies in the human genome, of which at least approximately 120 have evolved into bona fide genes. Among these, approximately 50 retrogenes have evolved functions in testes, more than half of which were recruited as functional autosomal counterparts of X-linked genes during spermatogenesis. Generally, retrogenes emerge "out of the testis," because they are often initially transcribed in testis and later evolve stronger and sometimes more diverse spatial expression patterns. We find a significant excess of transcribed retrocopies close to other genes or within introns, suggesting that retrocopies can exploit the regulatory elements and/or open chromatin of neighboring genes to become transcribed. In direct support of this hypothesis, we identify 36 retrocopy-host gene fusions, including primate-specific chimeric genes. Strikingly, 27 intergenic retrogenes have acquired untranslated exons de novo during evolution to achieve high expression levels. Notably, our screen for highly transcribed retrocopies also uncovered a retrogene linked to a human recessive disorder, gelatinous drop-like corneal dystrophy, a form of blindness. These functional implications for retroposition notwithstanding, we find that the insertion of retrocopies into genes is generally deleterious, because it may interfere with the transcription of host genes. Our results demonstrate that natural selection has been fundamental in shaping the retrocopy repertoire of the human genome.

Permanent correction of an inherited ectodermal dysplasia with recombinant EDA.

X-linked hypohidrotic ectodermal dysplasia (XLHED; OMIM 305100) is a genetic disorder characterized by absence or deficient function of hair, teeth and sweat glands. Affected children may experience life-threatening high fever resulting from reduced ability to sweat. Mice with the Tabby phenotype share many symptoms with human XLHED patients because both phenotypes are caused by mutations of the syntenic ectodysplasin A gene (Eda) on the X chromosome. Two main splice variants of Eda, encoding EDA1 and EDA2, engage the tumor necrosis factor (TNF) family receptors EDAR and XEDAR, respectively. The EDA1 protein, acting through EDAR, is essential for proper formation of skin appendages; the functions of EDA2 and XEDAR are not known. EDA1 must be proteolytically processed to a soluble form to be active. Here, we show that treatment of pregnant Tabby mice with a recombinant form of EDA1, engineered to cross the placental barrier, permanently rescues the Tabby phenotype in the offspring. Notably, sweat glands can also be induced by EDA1 after birth. This is the first example of a developmental genetic defect that can be permanently corrected by short-term treatment with a recombinant protein.

The Glucocorticoid-induced leucine zipper (GILZ) Is essential for spermatogonial survival and spermatogenesis.

Spermatogenesis relies on the precise regulation of the self-renewal and differentiation of spermatogonia to provide a continuous supply of differentiating germ cells. The understanding of the cellular pathways regulating this equilibrium remains unfortunately incomplete. This investigation aimed to elucidate the testicular and ovarian functions of the glucocorticoid-induced leucine zipper protein (GILZ) encoded by the X-linked Tsc22d3 (Gilz) gene. We found that GILZ is specifically expressed in the cytoplasm of proliferating spermatogonia and preleptotene spermatocytes. While Gilz mutant female mice were fully fertile, constitutive or male germ cell-specific ablation of Gilz led to sterility due to a complete absence of post-meiotic germ cells and mature spermatozoa. Alterations were observed as early as postnatal day 5 during the first spermatogenic wave and included extensive apoptosis at the spermatogonial level and meiotic arrest in the mid-late zygotene stage. Overall, these data emphasize the essential role played by GILZ in mediating spermatogonial survival and spermatogenesis.

Pulmonary involvement in Fabry disease: Overview and perspectives.

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by deficiency of alpha-galactosidase A, which leads to storage of sphingolipids in virtually all human cells and consequently to organ dysfunction. Pulmonary involvement is still debated. But, obstructive lung disease is up to ten times more prevalent in patients with FD compared to general public. Also, an accelerated decline in forced expiratory volume in one second (FEV1) over time was observed in these patients. Lysosomal storage of glycosphingolipids is considered leading to small airway disease via hyperplasia of the bronchiolar smooth muscle cells. Larger airways may become involved with ongoing disease process. There is no evidence for involvement of the lung interstitium in FD. The effect of enzyme replacement therapy on respiratory involvement remains to be determined in large, prospective controlled trials.