Amyotrophie spinale proximale de type Ia (caractérisation du phénotype pré- et postnatal à partir de 12 patients porteurs d un génotype 0SMN1/1SMN2)

L'amyotrophie spinale proximale (SMA) résulte de l'inactivation homozygote du gène SMN1. La sévérité de la maladie est inversement corrélée au nombre de copies du principal gène modificateur, le gène SMN2. Le génotype 0SMN1I1SMN2, très rare, est étroitement corrélé aux formes les plus sévères de SMA, appelées type Ia. L'objectif de ce travail est de décrire précisément le phénotype pré- et postnatal de la SMA de type la à partir des données recueillies pour 12 patients porteurs d'un génotype 0SMN1/1SMN2 répertoriés grâce à la banque de données nationale UMD-SMN1 et de 33 patients atteints de SMA de type Ta issus de la littérature. La SMA de type Ia se manifeste dès la naissance par une atteinte neurologique extrêmement sévère comportant atteinte respiratoire nécessitant une assistance ventilatoire immédiate, une hypotonie et un déficit musculaire global. Une atteinte du tronc cérébral (troubles de la succion/déglutition, atteinte faciale) et des signes d'immobilisme foetal (rétractions articulaires, micrognathisme, palais ogival) sont observés. L'éveil est le plus souvent conservé. Des malformations cardiaques sont fréquemment associées. La survie excède rarement un mois. Les signes en période anténatale sont quant à eux discrets et peu spécifiques. Une diminution des mouvements actifs foetaux au troisième trimestre de grossesse est fréquemment rapportée. Une hyperclarté nucale ou un hydramnios sont rapportés de manière inconstante. La SMA de type Ia se révèle extrêmement difficile à détecter en période anténatale. Compte-tenu de ces observations, des indications pour le diagnostic moléculaire de SMA en période anténatale peuvent toutefois être proposées.ROUEN-BU Médecine-Pharmacie (765402102) / SudocSudocFranceF

Loss-of-function and missense variants in NSD2 cause decreased methylation activity and are associated with a distinct developmental phenotype

PURPOSE: Despite a few recent reports of patients harboring truncating variants in NSD2, a gene considered critical for the Wolf–Hirschhorn syndrome (WHS) phenotype, the clinical spectrum associated with NSD2 pathogenic variants remains poorly understood. METHODS: We collected a comprehensive series of 18 unpublished patients carrying heterozygous missense, elongating, or truncating NSD2 variants; compared their clinical data to the typical WHS phenotype after pooling them with ten previously described patients; and assessed the underlying molecular mechanism by structural modeling and measuring methylation activity in vitro. RESULTS: The core NSD2-associated phenotype includes mostly mild developmental delay, prenatal-onset growth retardation, low body mass index, and characteristic facial features distinct from WHS. Patients carrying missense variants were significantly taller and had more frequent behavioral/psychological issues compared with those harboring truncating variants. Structural in silico modeling suggested interference with NSD2’s folding and function for all missense variants in known structures. In vitro testing showed reduced methylation activity and failure to reconstitute H3K36me2 in NSD2 knockout cells for most missense variants. CONCLUSION: NSD2 loss-of-function variants lead to a distinct, rather mild phenotype partially overlapping with WHS. To avoid confusion for patients, NSD2 deficiency may be named Rauch–Steindl syndrome after the delineators of this phenotype

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

Clinical spectrum of MTOR-related hypomelanosis of Ito with neurodevelopmental abnormalities.

PURPOSE: Hypomelanosis of Ito (HI) is a skin marker of somatic mosaicism. Mosaic MTOR pathogenic variants have been reported in HI with brain overgrowth. We sought to delineate further the pigmentary skin phenotype and clinical spectrum of neurodevelopmental manifestations of MTOR-related HI. METHODS: From two cohorts totaling 71 patients with pigmentary mosaicism, we identified 14 patients with Blaschko-linear and one with flag-like pigmentation abnormalities, psychomotor impairment or seizures, and a postzygotic MTOR variant in skin. Patient records, including brain magnetic resonance image (MRI) were reviewed. Immunostaining (n = 3) for melanocyte markers and ultrastructural studies (n = 2) were performed on skin biopsies. RESULTS: MTOR variants were present in skin, but absent from blood in half of cases. In a patient (p.[Glu2419Lys] variant), phosphorylation of p70S6K was constitutively increased. In hypopigmented skin of two patients, we found a decrease in stage 4 melanosomes in melanocytes and keratinocytes. Most patients (80%) had macrocephaly or (hemi)megalencephaly on MRI. CONCLUSION: MTOR-related HI is a recognizable neurocutaneous phenotype of patterned dyspigmentation, epilepsy, intellectual deficiency, and brain overgrowth, and a distinct subtype of hypomelanosis related to somatic mosaicism. Hypopigmentation may be due to a defect in melanogenesis, through mTORC1 activation, similar to hypochromic patches in tuberous sclerosis complex

A Solve-RD ClinVar-based reanalysis of 1522 index cases from ERN-ITHACA reveals common pitfalls and misinterpretations in exome sequencing

Purpose Within the Solve-RD project (https://solve-rd.eu/), the European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies aimed to investigate whether a reanalysis of exomes from unsolved cases based on ClinVar annotations could establish additional diagnoses. We present the results of the “ClinVar low-hanging fruit” reanalysis, reasons for the failure of previous analyses, and lessons learned. Methods Data from the first 3576 exomes (1522 probands and 2054 relatives) collected from European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies was reanalyzed by the Solve-RD consortium by evaluating for the presence of single-nucleotide variant, and small insertions and deletions already reported as (likely) pathogenic in ClinVar. Variants were filtered according to frequency, genotype, and mode of inheritance and reinterpreted. Results We identified causal variants in 59 cases (3.9%), 50 of them also raised by other approaches and 9 leading to new diagnoses, highlighting interpretation challenges: variants in genes not known to be involved in human disease at the time of the first analysis, misleading genotypes, or variants undetected by local pipelines (variants in off-target regions, low quality filters, low allelic balance, or high frequency). Conclusion The “ClinVar low-hanging fruit” analysis represents an effective, fast, and easy approach to recover causal variants from exome sequencing data, herewith contributing to the reduction of the diagnostic deadlock

Amyotrophie spinale proximale de type Ia : caractérisation du phénotype pré- et postnatal à partir de 12 patients porteurs d'un génotype 0SMN1/1SMN2

L'amyotrophie spinale proximale (SMA) résulte de l'inactivation homozygote du gène SMN1. La sévérité de la maladie est inversement corrélée au nombre de copies du principal gène modificateur, le gène SMN2. Le génotype 0SMN1I1SMN2, très rare, est étroitement corrélé aux formes les plus sévères de SMA, appelées type Ia. L'objectif de ce travail est de décrire précisément le phénotype pré- et postnatal de la SMA de type la à partir des données recueillies pour 12 patients porteurs d'un génotype 0SMN1/1SMN2 répertoriés grâce à la banque de données nationale UMD-SMN1 et de 33 patients atteints de SMA de type Ta issus de la littérature. La SMA de type Ia se manifeste dès la naissance par une atteinte neurologique extrêmement sévère comportant atteinte respiratoire nécessitant une assistance ventilatoire immédiate, une hypotonie et un déficit musculaire global. Une atteinte du tronc cérébral (troubles de la succion/déglutition, atteinte faciale) et des signes d'immobilisme foetal (rétractions articulaires, micrognathisme, palais ogival) sont observés. L'éveil est le plus souvent conservé. Des malformations cardiaques sont fréquemment associées. La survie excède rarement un mois. Les signes en période anténatale sont quant à eux discrets et peu spécifiques. Une diminution des mouvements actifs foetaux au troisième trimestre de grossesse est fréquemment rapportée. Une hyperclarté nucale ou un hydramnios sont rapportés de manière inconstante. La SMA de type Ia se révèle extrêmement difficile à détecter en période anténatale. Compte-tenu de ces observations, des indications pour le diagnostic moléculaire de SMA en période anténatale peuvent toutefois être proposées

Clinical impact of post-mortem genetic testing in cardiac death and cardiomyopathy

International audiencePost-mortem genetic analyses may help to elucidate the cause of cardiac death. The added value is however unclear when a cardiac disease is already suspected or affirmed. Our aim was to study the feasibility and medical impact of post-mortem genetic analyses in suspected cardiomyopathy. We studied 35 patients with cardiac death and suspected cardiomyopathy based on autopsy or clinical data. After targeted sequencing, we identified 15 causal variants in 15 patients (yield 43%) in sarcomeric (n = 8), desmosomal (n = 3), lamin A/C (n = 3) and transthyretin (n = 1) genes. The results had various impacts on families, i.e. allowed predictive genetic testing in relatives (15 families), planned early therapeutics based on the specific underlying gene (5 families), rectified the suspected cardiomyopathy subtype (2 families), assessed the genetic origin of cardiomyopathy that usually has an acquired cause (1 family), assessed the diagnosis in a patient with uncertain borderline cardiomyopathy (1 family), reassured the siblings because of a de novo mutation (2 families) and allowed prenatal testing (1 family). Our findings suggest that post-mortem molecular testing should be included in the strategy of family care after cardiac death and suspected cardiomyopathy, since genetic findings provide additional information useful for relatives, which are beyond conventional autopsy

Clinical impact of post-mortem genetic testing in cardiac death and cardiomyopathy

Post-mortem genetic analyses may help to elucidate the cause of cardiac death. The added value is however unclear when a cardiac disease is already suspected or affirmed. Our aim was to study the feasibility and medical impact of post-mortem genetic analyses in suspected cardiomyopathy. We studied 35 patients with cardiac death and suspected cardiomyopathy based on autopsy or clinical data. After targeted sequencing, we identified 15 causal variants in 15 patients (yield 43%) in sarcomeric (n = 8), desmosomal (n = 3), lamin A/C (n = 3) and transthyretin (n = 1) genes. The results had various impacts on families, i.e. allowed predictive genetic testing in relatives (15 families), planned early therapeutics based on the specific underlying gene (5 families), rectified the suspected cardiomyopathy subtype (2 families), assessed the genetic origin of cardiomyopathy that usually has an acquired cause (1 family), assessed the diagnosis in a patient with uncertain borderline cardiomyopathy (1 family), reassured the siblings because of a de novo mutation (2 families) and allowed prenatal testing (1 family). Our findings suggest that post-mortem molecular testing should be included in the strategy of family care after cardiac death and suspected cardiomyopathy, since genetic findings provide additional information useful for relatives, which are beyond conventional autopsy

Novel missense mutations in PTCHD1 alter its plasma membrane subcellular localization and cause intellectual disability and autism spectrum disorder

International audienceThe X-linked PTCHD1 gene, encoding a synaptic membrane protein, has been involved in neurodevelopmental disorders with the description of deleterious genomic microdeletions or truncating coding mutations. Missense variants were also identified, however, without any functional evidence supporting their pathogenicity level. We investigated 13 missense variants of PTCHD1, including eight previously described (c.152G>A,p.(Ser51Asn); c.217C>T,p.(Leu73Phe); c.517A>G,p.(Ile173Val); c.542A>C,p.(Lys181Thr); c.583G>A,p.(Val195Ile); c.1076A>G,p.(His359Arg); c.1409C>A,p.(Ala470Asp); c.1436A>G,p.(Glu479Gly)), and five novel ones (c.95C>T,p.(Pro32Leu); c.95C>G,p.(Pro32Arg); c.638A>G,p.(Tyr213Cys); c.898G>C,p.(Gly300Arg); c.928G>C,p.(Ala310Pro)) identified in male patients with intellectual disability (ID) and/or autism spectrum disorder (ASD). Interestingly, several of these variants involve amino acids localized in structural domains such as transmembrane segments. To evaluate their potentially deleterious impact on PTCHD1 protein function, we performed in vitro overexpression experiments of the wild-type and mutated forms of PTCHD1-GFP in HEK 293T and in Neuro-2a cell lines as well as in mouse hippocampal primary neuronal cultures. We found that six variants impaired the expression level of the PTCHD1 protein, and were retained in the endoplasmic reticulum suggesting abnormal protein folding. Our functional analyses thus provided evidence of the pathogenic impact of missense variants in PTCHD1, which reinforces the involvement of the PTCHD1 gene in ID and in ASD

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

International audienc