Biology subjects

Isidor, B.

Publications and source records attributed to Isidor, B..

3 recordsLinked to original sources

bioRxiv2018

Pathogenic DDX3X mutations impair RNA metabolism and neurogenesis during fetal cortical development

De novo germline mutations in the RNA helicase DDX3X account for 1-3% of unexplained intellectual disability (ID) cases in females, and are associated with autism, brain malformations, and epilepsy. Yet, the developmental and molecular mechanisms by which DDX3X mutations impair brain function are unknown. Here we use human and mouse genetics, and cell biological and biochemical approaches to elucidate mechanisms by which pathogenic DDX3X variants disrupt brain development. We report the largest clinical cohort to date with DDX3X mutations (n=78), demonstrating a striking correlation between recurrent dominant missense mutations, polymicrogyria, and the most severe clinical outcomes. We show that Ddx3x controls cortical development by regulating neuronal generation and migration. Severe DDX3X missense mutations profoundly disrupt RNA helicase activity and induce ectopic RNA-protein granules and aberrant translation in neural progenitors and neurons. Together, our study demonstrates novel mechanisms underlying DDX3X syndrome, and highlights roles for RNA-protein aggregates in the pathogenesis of neurodevelopmental disease.

genetics↗

bioRxiv2017

Duplications at 19q13.33 in patients with neurodevelopmental disorders

OBJECTIVEAfter recent publication of the first patients with disease associated missense variants in GRIN2D, we evaluate the effect of copy number variation (CNV) overlapping this gene towards the presentation of neurodevelopmental disorders.\n\nMETHODSWe explored ClinVar (N{degrees}CNV = 41,398) and DECIPHER (N{degrees}CNV = 30,222) clinical databases of genomic variations for patients with copy number changes overlapping the GRIN2D gene at the 19q13.33 locus and evaluated their respective phenotype alongside their frequency, gene content and expression with publicly available reference databases.\n\nRESULTSWe identified 13 patients with microduplications at the 19q13.33 locus. The majority of CNVs arose de novo and comparable CNVs are not present in control databases. All patients were reported to have neurodevelopmental disorders and dysmorphic features as the most common clinical phenotype (N= 10/13), followed by seizures (N= 6/13) and intellectual disability (N= 5/13). All duplications shared a consensus region of 405 kb overlapping 13 genes. After screening for duplication tolerance in control populations, positive gene brain expression and gene dosage sensitivity analysis, we highlight four genes for future evaluation: CARD8, C19orf68, KDELR1 and GRIN2D, which are promising candidates for disease causality. Further, investigation of the literature especially supports GRIN2D as the best candidate gene.\n\nCONCLUSIONSOur study presents dup19q13.33 as novel duplication syndrome locus associated with neurodevelopmental disorders. CARD8, C19orf68, KDELR1 and GRIN2D are promising candidates for functional follow up.

genetics↗

bioRxiv2017

A framework to identify modifier genes in patients with Phelan-McDermid syndrome

Phelan-McDermid syndrome (PMS) is characterized by a variety of clinical symptoms with heterogeneous degrees of severity, including intellectual disability, speech impairment, and autism spectrum disorders (ASD). It results from a deletion of the 22q13 locus that in most cases includes the SHANK3 gene. SHANK3 is considered a major gene for PMS, but the factors modulating the severity of the syndrome remain largely unknown. In this study, we investigated 85 PMS patients with different 22q13 rearrangements (78 deletions, 7 duplications). We first explored their clinical features and provide evidence for frequent corpus callosum abnormalities. We then mapped candidate genomic regions at the 22q13 locus associated with risk of clinical features, and suggest a second locus associated with absence of speech. Finally, in some cases, we identified additional rearrangements at loci associated with ASD, potentially modulating the severity of the syndrome. We also report the first SHANK3 deletion transmitted to five affected daughters by a mother without intellectual disability nor ASD, suggesting that some individuals could compensate for such mutations. In summary, we shed light on the genotype-phenotype relationship of PMS, a step towards the identification of compensatory mechanisms for a better prognosis and possibly treatments of patients with neurodevelopmental disorders.

genetics↗