Mechanism of KMT5B haploinsufficiency in neurodevelopment in humans and mice.

Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest (n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.

De novo coding variants in the AGO1 gene cause a neurodevelopmental disorder with intellectual disability.

BACKGROUND: High-impact pathogenic variants in more than a thousand genes are involved in Mendelian forms of neurodevelopmental disorders (NDD). METHODS: This study describes the molecular and clinical characterisation of 28 probands with NDD harbouring heterozygous AGO1 coding variants, occurring de novo for all those whose transmission could have been verified (26/28). RESULTS: A total of 15 unique variants leading to amino acid changes or deletions were identified: 12 missense variants, two in-frame deletions of one codon, and one canonical splice variant leading to a deletion of two amino acid residues. Recurrently identified variants were present in several unrelated individuals: p.(Phe180del), p.(Leu190Pro), p.(Leu190Arg), p.(Gly199Ser), p.(Val254Ile) and p.(Glu376del). AGO1 encodes the Argonaute 1 protein, which functions in gene-silencing pathways mediated by small non-coding RNAs. Three-dimensional protein structure predictions suggest that these variants might alter the flexibility of the AGO1 linker domains, which likely would impair its function in mRNA processing. Affected individuals present with intellectual disability of varying severity, as well as speech and motor delay, autistic behaviour and additional behavioural manifestations. CONCLUSION: Our study establishes that de novo coding variants in AGO1 are involved in a novel monogenic form of NDD, highly similar to the recently reported AGO2-related NDD.

Primrose syndrome: a phenotypic comparison of patients with a ZBTB20 missense variant versus a 3q13.31 microdeletion including ZBTB20.

Primrose syndrome is characterized by variable intellectual deficiency, behavior disorders, facial features with macrocephaly, and a progressive phenotype with hearing loss and ectopic calcifications, distal muscle wasting, and contractures. In 2014, ZBTB20 variants were identified as responsible for this syndrome. Indeed, ZBTB20 plays an important role in cognition, memory, learning processes, and has a transcription repressive effect on numerous genes. A more severe phenotype was discussed in patients with missense single nucleotide variants than in those with large deletions. Here, we report on the clinical and molecular results of 14 patients: 6 carrying ZBTB20 missense SNVs, 1 carrying an early truncating indel, and 7 carrying 3q13.31 deletions, recruited through the AnDDI-Rares network. We compared their phenotypes and reviewed the data of the literature, in order to establish more powerful phenotype-genotype correlations. All 57 patients presented mild-to-severe ID and/or a psychomotor delay. Facial features were similar with macrocephaly, prominent forehead, downslanting palpebral fissures, ptosis, and large ears. Hearing loss was far more frequent in patients with missense SNVs (p = 0.002), ectopic calcification, progressive muscular wasting, and contractures were observed only in patients with missense SNVs (p nonsignificant). Corpus callosum dysgenesis (p = 0.00004), hypothyroidism (p = 0.047), and diabetes were also more frequent in this group. However, the median age was 9.4 years in patients with deletions and truncating variant compared with 15.1 years in those with missense SNVs. Longer follow-up will be necessary to determine whether the phenotype of patients with deletions is also progressive.

Exome sequencing identifies the first genetic determinants of sirenomelia in humans.

Sirenomelia is a rare severe malformation sequence of unknown cause characterized by fused legs and severe visceral abnormalities. We present a series of nine families including two rare familial aggregations of sirenomelia investigated by a trio-based exome sequencing strategy. This approach identified CDX2 variants in the two familial aggregations, both fitting an autosomal dominant pattern of inheritance with variable expressivity. CDX2 is a major regulator of caudal development in vertebrate and mouse heterozygotes are a previously described model of sirenomelia. Remarkably, the p.(Arg237His) variant has already been reported in a patient with persistent cloaca. Analysis of the sporadic cases revealed six additional candidate variants including a de novo frameshift variant in the genetically constrained NKD1 gene, encoding a known interactor of CDX2. We provide the first insights for a genetic contribution in human sirenomelia and highlight the role of Cdx and Wnt signaling pathways in the development of this disorder.

Hearing loss in inherited peripheral neuropathies: Molecular diagnosis by NGS in a French series.

BACKGROUND: The most common inherited peripheral neuropathy is Charcot-Marie-Tooth disease (CMT), with a prevalence of 1/2500. Other symptoms can be associated to the condition, such as hearing loss. Currently, no global hearing impairment assessment has been determined, and the physiopathology is not well known. METHODS: The aim of the study was to analyze among a French series of 3,412 patients with inherited peripheral neuropathy (IPN), the ones who also suffer from hearing loss, to establish phenotype-genotype correlations. An NGS strategy for IPN one side and nonsyndromic hearing loss (NSHL) on the other side, were performed. RESULTS: Hearing loss (HL) was present in only 44 patients (1.30%). The clinical data of 27 patients were usable. Demyelinating neuropathy was diagnosed in 15 cases and axonal neuropathy in 12 cases. HL varied from mild to profound. Five cases of auditory neuropathy were noticed. Diagnosis was made for 60% of these patients. Seven novel pathogenic variants were discovered in five different genes: PRPS1; MPZ; SH3TC2; NEFL; and ABHD12. Two patients with PMP22 variant, had also an additional variant in COCH and MYH14 respectively. No pathogenic variant was found at the DFNB1 locus. Genotype-phenotype correlations do exist, especially with SH3TC2, PRPS1, ABHD12, NEFL, and TRPV4. CONCLUSION: Involvement of PMP22 is not enough to explain hearing loss in patients suffering from IPN. HL can be due to cochlear impairment and/or auditory nerve dysfunction. HL is certainly underdiagnosed, and should be evaluated in every patient suffering from IPN.

Diagnosis and management of individuals with Fetal Valproate Spectrum Disorder; a consensus statement from the European Reference Network for Congenital Malformations and Intellectual Disability.

BACKGROUND: A pattern of major and minor congenital anomalies, facial dysmorphic features, and neurodevelopmental difficulties, including cognitive and social impairments has been reported in some children exposed to sodium valproate (VPA) during pregnancy. Recognition of the increased risks of in utero exposure to VPA for congenital malformations, and for the neurodevelopmental effects in particular, has taken many years but these are now acknowledged following the publication of the outcomes of several prospective studies and registries. As with other teratogens, exposure to VPA can have variable effects, ranging from a characteristic pattern of major malformations and significant intellectual disability to the other end of the continuum, characterised by facial dysmorphism which is often difficult to discern and a more moderate effect on neurodevelopment and general health. It has become clear that some individuals with FVSD have complex needs requiring multidisciplinary care but information regarding management is currently lacking in the medical literature. METHODS: An expert group was convened by ERN-ITHACA, the European Reference Network for Congenital Malformations and Intellectual Disability comprised of professionals involved in the care of individuals with FVSD and with patient representation. Review of published and unpublished literature concerning management of FVSD was undertaken and the level of evidence from these sources graded. Management recommendations were made based on strength of evidence and consensus expert opinion, in the setting of an expert consensus meeting. These were then refined using an iterative process and wider consultation. RESULTS: Whilst there was strong evidence regarding the increase in risk for major congenital malformations and neurodevelopmental difficulties there was a lack of high level evidence in other areas and in particular in terms of optimal clinical management.. The expert consensus approach facilitated the formulation of management recommendations, based on literature evidence and best practice. The outcome of the review and group discussions leads us to propose the term Fetal Valproate Spectrum Disorder (FVSD) as we feel this better encompasses the broad range of effects seen following VPA exposure in utero. CONCLUSION: The expert consensus approach can be used to define the best available clinical guidance for the diagnosis and management of rare disorders such as FVSD. FVSD can have medical, developmental and neuropsychological impacts with life-long consequences and affected individuals benefit from the input of a number of different health professionals.

Clinical study of 19 patients with SCN8A-related epilepsy: Two modes of onset regarding EEG and seizures.

OBJECTIVE: To describe the mode of onset of SCN8A-related severe epilepsy in order to facilitate early recognition, and eventually early treatment with sodium channel blockers. METHODS: We reviewed the phenotype of patients carrying a mutation in the SCN8A gene, among a multicentric cohort of 638 patients prospectively followed by several pediatric neurologists. We focused on the way clinicians made the diagnosis of epileptic encephalopathy, the very first symptoms, electroencephalography (EEG) findings, and seizure types. We made genotypic/phenotypic correlation based on epilepsy-associated missense variant localization over the protein. RESULTS: We found 19 patients carrying a de novo mutation of SCN8A, representing 3% of our cohort, with 9 mutations being novel. Age at onset of epilepsy was 1 day to 16 months. We found two modes of onset: 12 patients had slowly emerging onset with rare and/or subtle seizures and normal interictal EEG (group 1). The first event was either acute generalized tonic-clonic seizure (GTCS; Group 1a, n = 6) or episodes of myoclonic jerks that were often mistaken for sleep-related movements or other movement disorders (Group 1b, n = 6). Seven patients had a sudden onset of frequent tonic seizures or epileptic spasms with abnormal interictal EEG leading to rapid diagnosis of epileptic encephalopathy. Sodium channel blockers were effective or nonaggravating in most cases. SIGNIFICANCE: SCN8A is the third most prevalent early onset epileptic encephalopathy gene and is associated with two modes of onset of epilepsy.

Targeted panel sequencing establishes the implication of planar cell polarity pathway and involves new candidate genes in neural tube defect disorders.

Neural tube defect disorders are developmental diseases that originate from an incomplete closure of the neural tube during embryogenesis. Despite high prevalence-1 out of 3000 live births-their etiology is not yet established and both environmental and genetic factors have been proposed, with a heritability rate of about 60%. Studies in mouse models as well as in human have further suggested a multifactorial pattern of inheritance for neural tube defect disorders. Here, we report results obtained from clinical diagnosis and NGS analysis of a cohort composed of 52 patients. Using a candidate gene panel approach, we identified variants in known genes of planar cell polarity (PCP) pathway, although with higher prevalence than previously reported. Our study also reveals variants in novel genes such as FREM2 and DISP1. Altogether, these results confirm the implication of the PCP genes and involve the FRAS/FREM2 complex and Sonic Hedgehog signaling as novel components in the appearance of NTDs.

A large multicenter study of pediatric myotonic dystrophy type 1 for evidence-based management.

OBJECTIVE: To genotypically and phenotypically characterize a large pediatric myotonic dystrophy type 1 (DM1) cohort to provide a solid frame of data for future evidence-based health management. METHODS: Among the 2,697 patients with genetically confirmed DM1 included in the French DM-Scope registry, children were enrolled between January 2010 and February 2016 from 24 centers. Comprehensive cross-sectional analysis of most relevant qualitative and quantitative variables was performed. RESULTS: We studied 314 children (52% females, with 55% congenital, 31% infantile, 14% juvenile form). The age at inclusion was inversely correlated with the CTG repeat length. The paternal transmission rate was higher than expected, especially in the congenital form (13%). A continuum of highly prevalent neurodevelopmental alterations was observed, including cognitive slowing (83%), attention deficit (64%), written language (64%), and spoken language (63%) disorders. Five percent exhibited autism spectrum disorders. Overall, musculoskeletal impairment was mild. Despite low prevalence, cardiorespiratory impairment could be life-threatening, and frequently occurred early in the first decade (25.9%). Gastrointestinal symptoms (27%) and cataracts (7%) were more frequent than expected, while endocrine or metabolic disorders were scarce. CONCLUSIONS: The pedDM-Scope study details the main genotype and phenotype characteristics of the 3 DM1 pediatric subgroups. It highlights striking profiles that could be useful in health care management (including transition into adulthood) and health policy planning.

Heterozygous loss-of-function variants of MEIS2 cause a triad of palatal defects, congenital heart defects, and intellectual disability.

Deletions on chromosome 15q14 are a known chromosomal cause of cleft palate, typically co-occurring with intellectual disability, facial dysmorphism, and congenital heart defects. The identification of patients with loss-of-function variants in MEIS2, a gene within this deletion, suggests that these features are attributed to haploinsufficiency of MEIS2. To further delineate the phenotypic spectrum of the MEIS2-related syndrome, we collected 23 previously unreported patients with either a de novo sequence variant in MEIS2 (9 patients), or a 15q14 microdeletion affecting MEIS2 (14 patients). All but one de novo MEIS2 variant were identified by whole-exome sequencing. One variant was found by targeted sequencing of MEIS2 in a girl with a clinical suspicion of this syndrome. In addition to the triad of palatal defects, heart defects, and developmental delay, heterozygous loss of MEIS2 results in recurrent facial features, including thin and arched eyebrows, short alae nasi, and thin vermillion. Genotype-phenotype comparison between patients with 15q14 deletions and patients with sequence variants or intragenic deletions within MEIS2, showed a higher prevalence of moderate-to-severe intellectual disability in the former group, advocating for an independent locus for psychomotor development neighboring MEIS2.

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

PURPOSE: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences. METHODS: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms. RESULTS: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments. CONCLUSION: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.

Mutations in the SRP54 gene cause severe congenital neutropenia as well as Shwachman-Diamond-like syndrome.

Congenital neutropenias (CNs) are rare heterogeneous genetic disorders, with about 25% of patients without known genetic defects. Using whole-exome sequencing, we identified a heterozygous mutation in the SRP54 gene, encoding the signal recognition particle (SRP) 54 GTPase protein, in 3 sporadic cases and 1 autosomal dominant family. We subsequently sequenced the SRP54 gene in 66 probands from the French CN registry. In total, we identified 23 mutated cases (16 sporadic, 7 familial) with 7 distinct germ line SRP54 mutations including a recurrent in-frame deletion (Thr117del) in 14 cases. In nearly all patients, neutropenia was chronic and profound with promyelocytic maturation arrest, occurring within the first months of life, and required long-term granulocyte colony-stimulating factor therapy with a poor response. Neutropenia was sometimes associated with a severe neurodevelopmental delay (n = 5) and/or an exocrine pancreatic insufficiency requiring enzyme supplementation (n = 3). The SRP54 protein is a key component of the ribonucleoprotein complex that mediates the co-translational targeting of secretory and membrane proteins to the endoplasmic reticulum (ER). We showed that SRP54 was specifically upregulated during the in vitro granulocytic differentiation, and that SRP54 mutations or knockdown led to a drastically reduced proliferation of granulocytic cells associated with an enhanced P53-dependent apoptosis. Bone marrow examination of SRP54-mutated patients revealed a major dysgranulopoiesis and features of cellular ER stress and autophagy that were confirmed using SRP54-mutated primary cells and SRP54 knockdown cells. In conclusion, we characterized a pathological pathway, which represents the second most common cause of CN with maturation arrest in the French CN registry.

Further delineation of the MECP2 duplication syndrome phenotype in 59 French male patients, with a particular focus on morphological and neurological features.

The Xq28 duplication involving the MECP2 gene (MECP2 duplication) has been mainly described in male patients with severe developmental delay (DD) associated with spasticity, stereotypic movements and recurrent infections. Nevertheless, only a few series have been published. We aimed to better describe the phenotype of this condition, with a focus on morphological and neurological features. Through a national collaborative study, we report a large French series of 59 affected males with interstitial MECP2 duplication. Most of the patients (93%) shared similar facial features, which evolved with age (midface hypoplasia, narrow and prominent nasal bridge, thick lower lip, large prominent ears), thick hair, livedo of the limbs, tapered fingers, small feet and vasomotor troubles. Early hypotonia and global DD were constant, with 21% of patients unable to walk. In patients able to stand, lower limbs weakness and spasticity led to a singular standing habitus: flexion of the knees, broad-based stance with pseudo-ataxic gait. Scoliosis was frequent (53%), such as divergent strabismus (76%) and hypermetropia (54%), stereotypic movements (89%), without obvious social withdrawal and decreased pain sensitivity (78%). Most of the patients did not develop expressive language, 35% saying few words. Epilepsy was frequent (59%), with a mean onset around 7.4 years of age, and often (62%) drug-resistant. Other medical issues were frequent: constipation (78%), and recurrent infections (89%), mainly lung. We delineate the clinical phenotype of MECP2 duplication syndrome in a large series of 59 males. Pulmonary hypertension appeared as a cause of early death in these patients, advocating its screening early in life.

Mutations in GREB1L Cause Bilateral Kidney Agenesis in Humans and Mice.

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute a major cause of chronic kidney disease in children and 20% of prenatally detected anomalies. CAKUT encompass a spectrum of developmental kidney defects, including renal agenesis, hypoplasia, and cystic and non-cystic dysplasia. More than 50 genes have been reported as mutated in CAKUT-affected case subjects. However, the pathophysiological mechanisms leading to bilateral kidney agenesis (BKA) remain largely elusive. Whole-exome or targeted exome sequencing of 183 unrelated familial and/or severe CAKUT-affected case subjects, including 54 fetuses with BKA, led to the identification of 16 heterozygous variants in GREB1L (growth regulation by estrogen in breast cancer 1-like), a gene reported as a target of retinoic acid signaling. Four loss-of-function and 12 damaging missense variants, 14 being absent from GnomAD, were identified. Twelve of them were present in familial or simplex BKA-affected case subjects. Female BKA-affected fetuses also displayed uterus agenesis. We demonstrated a significant association between GREB1L variants and BKA. By in situ hybridization, we showed expression of Greb1l in the nephrogenic zone in developing mouse kidney. We generated a Greb1l knock-out mouse model by CRISPR-Cas9. Analysis at E13.5 revealed lack of kidneys and genital tract anomalies in male and female Greb1l-/- embryos and a slight decrease in ureteric bud branching in Greb1l+/- embryos. We showed that Greb1l invalidation in mIMCD3 cells affected tubulomorphogenesis in 3D-collagen culture, a phenotype rescued by expression of the wild-type human protein. This demonstrates that GREB1L plays a major role in early metanephros and genital development in mice and humans.

Outcomes of intra-detrusor injections of botulinum toxin in patients with spina bifida: A systematic review.

CONTEXT: Bladder management in spina bifida patients relies on clean intermittent catheterization and oral antimuscarinics with a significant failure rate. The efficacy of intradetrusor injections of botulinum toxin has been confirmed in patients with spinal cord injury or multiple sclerosis but not in patients with myelomeningocele. OBJECTIVE: To conduct a systematic review of current evidence regarding the efficacy of intra-detrusor injections of Botulinum Toxin A (BTX-A) in spina bifida patients with neurogenic detrusor overactivity (NDO) refractory to antimuscarinics. METHODS: A research has been conducted on Medline and Embase using the keywords: ("spina bifida" OR "myelomeningocele" OR "dysraphism") AND "toxin." The search strategy and studies selection were performed using the PICOS method according to the PRISMA statement. RESULT: Twelve published series were included (n = 293 patients). All patients were <18 years old. There was no randomized study comparing BTX-A versus placebo and most studies had no control group. Most studies reported a clinical and urodynamic improvement with resolution of incontinence in 32-100% of patients, a decrease in maximum detrusor pressure from 32 to 54%, an increase of maximum cystometric capacity from 27 to 162%, and an improvement in bladder compliance of 28-176%. Two studies suggested lower efficacy in patients with low compliance bladder compared to those with isolated detrusor overactivity. CONCLUSION: Intradetrusor injections of BTX-A could be effective in children with spina bifida but this assumption is not supported by high level of evidence studies. There is no data available in adult patients. Neurourol. Urodynam. 36:557-564, 2017. © 2016 Wiley Periodicals, Inc.

Type 0 Spinal Muscular Atrophy: Further Delineation of Prenatal and Postnatal Features in 16 Patients.

BACKGROUND: Spinal muscular atrophy (SMA) is caused by homozygous inactivation of the SMN1 gene. The SMN2 copy number modulates the severity of SMA. The 0SMN1/1SMN2 genotype, the most severe genotype compatible with life, is expected to be associated with the most severe form of the disease, called type 0 SMA, defined by prenatal onset. OBJECTIVE: The aim of the study was to review clinical features and prenatal manifestations in this rare SMA subtype. METHODS: SMA patients with the 0SMN1/1SMN2 genotype were retrospectively collected using the UMD-SMN1 France database. RESULTS: Data from 16 patients were reviewed. These 16 patients displayed type 0 SMA. At birth, a vast majority had profound hypotonia, severe muscle weakness, severe respiratory distress, and cranial nerves involvement (inability to suck/swallow, facial muscles weakness). They showed characteristics of fetal akinesia deformation sequence and congenital heart defects. Recurrent episodes of bradycardia were observed. Death occurred within the first month. At prenatal stage, decreased fetal movements were frequently reported, mostly only by mothers, in late stages of pregnancy; increased nuchal translucency was reported in about half of the cases; congenital heart defects, abnormal amniotic fluid volume, or joint contractures were occasionally reported. CONCLUSION: Despite a prenatal onset attested by severity at birth and signs of fetal akinesia deformation sequence, prenatal manifestations of type 0 SMA are not specific and not constant. As illustrated by the frequent association with congenital heart defects, type 0 SMA physiopathology is not restricted to motor neuron, highlighting that SMN function is critical for organogenesis.

Otopalatodigital spectrum disorders: refinement of the phenotypic and mutational spectrum.

Otopalatodigital spectrum disorders (OPDSD) constitute a group of dominant X-linked osteochondrodysplasias including four syndromes: otopalatodigital syndromes type 1 and type 2 (OPD1 and OPD2), frontometaphyseal dysplasia, and Melnick-Needles syndrome. These syndromes variably associate specific facial and extremities features, hearing loss, cleft palate, skeletal dysplasia and several malformations, and show important clinical overlap over the different entities. FLNA gain-of-function mutations were identified in these conditions. FLNA encodes filamin A, a scaffolding actin-binding protein. Here, we report phenotypic descriptions and molecular results of FLNA analysis in a large series of 27 probands hypothesized to be affected by OPDSD. We identified 11 different missense mutations in 15 unrelated probands (n=15/27, 56%), of which seven were novel, including one of unknown significance. Segregation analyses within families made possible investigating 20 additional relatives carrying a mutation. This series allows refining the phenotypic and mutational spectrum of FLNA mutations causing OPDSD, and providing suggestions to avoid the overdiagnosis of OPD1.

Karyotype is not dead (yet)!

BACKGROUND: While array-comparative genomic hybridization (a-CGH) and next-generation sequencing (NGS or exome) technologies have swiftly spread throughout the medical field, karyotype has gradually lost its leading role among genetic tests. Several international guidelines recommend starting with a-CGH screening then going on with exome analysis when investigating a patient with intellectual disability (ID) and no precise clinical diagnosis. A-CGH and whole exome sequencing increase etiologic diagnoses rate up to 30% in case of ID. However, physicians have to deal with the lack of qualitative information of the genome. Especially, exome and a-CGH analysis fail to detect chromosomal rearrangements because breakpoints are either located in introns or not associated with a gain or loss of genetic material. If these technologies cannot easily identify chromosomal translocations or inversions which sometimes split a gene, karyotype can. DISCUSSION: For the 5 cases described, karyotype provided the right diagnosis for a Mendelian disease while molecular analysis remained unsuccessful. We conclude that when a Mendelian disease is strongly suggested clinically, if molecular analysis is normal, it could be very useful to carry out a karyotype in order to demonstrate a chromosomal rearrangement involving the targeted gene. If this gene is disrupted, the physician can confirm the suspected disease and give appropriate genetic counseling. SUMMARY: This article aims at keeping in mind that karyotype, this old-fashioned genetic tool, can still remain powerful and useful within some genetic issues. Even in this modern period of whole exome sequencing, young geneticists should know that karyotype remains a powerful and cheap technology, available throughout the world and can still do a lot for families.

Large national series of patients with Xq28 duplication involving MECP2: Delineation of brain MRI abnormalities in 30 affected patients.

Xq28 duplications encompassing MECP2 have been described in male patients with a severe neurodevelopmental disorder associated with hypotonia and spasticity, severe learning disability, stereotyped movements, and recurrent pulmonary infections. We report on standardized brain magnetic resonance imaging (MRI) data of 30 affected patients carrying an Xq28 duplication involving MECP2 of various sizes (228 kb to 11.7 Mb). The aim of this study was to seek recurrent malformations and attempt to determine whether variations in imaging features could be explained by differences in the size of the duplications. We showed that 93% of patients had brain MRI abnormalities such as corpus callosum abnormalities (n = 20), reduced volume of the white matter (WM) (n = 12), ventricular dilatation (n = 9), abnormal increased hyperintensities on T2-weighted images involving posterior periventricular WM (n = 6), and vermis hypoplasia (n = 5). The occipitofrontal circumference varied considerably between >+2SD in five patients and <-2SD in four patients. Among the nine patients with dilatation of the lateral ventricles, six had a duplication involving L1CAM. The only patient harboring bilateral posterior subependymal nodular heterotopia also carried an FLNA gene duplication. We could not demonstrate a correlation between periventricular WM hyperintensities/delayed myelination and duplication of the IKBKG gene. We thus conclude that patients with an Xq28 duplication involving MECP2 share some similar but non-specific brain abnormalities. These imaging features, therefore, could not constitute a diagnostic clue. The genotype-phenotype correlation failed to demonstrate a relationship between the presence of nodular heterotopia, ventricular dilatation, WM abnormalities, and the presence of FLNA, L1CAM, or IKBKG, respectively, in the duplicated segment.