Project description:We identified a missense variant in PSMD12 gene, recently associated to an emerging syndromic form of NDD, in a patient with intellectual disability/speech delay, congenital anomalies and facial dysmorphisms. The variant described herein is useful to expand the molecular spectrum of heterozygous PSMD12 mutations and to provide insight into the molecular pathogenesis of this new condition since it is, to the best of our knowledge, the first missense substitution to date reported in medical literature. Finally, our patient is the one with the most detailed dysmorphic characterization and for this reason useful to start defining a typical facial gestalt that addresses the diagnosis.
Project description:Chromatin remodeling is a dynamic epigenetic process that alters chromatin structure to gauge gene accessibility, enabling precise spatiotemporal gene expression, with disruptions often underlying neurodevelopmental disorders (NDDs), although the mechanistic underpinning remains incompletely understood. Despite essential roles in chromatin remodeling processes such as DNA methylation, and histone acetylation and deposition, DMAP1 has not been implicated in human disease. We identified 20 individuals from 16 families with a syndromic NDD carrying homozygous or compound heterozygous variants in DMAP1. Neural-specific knockdown of its Drosophila ortholog, dDMAP1, caused pupal lethality, structural defects in the mushroom body (MB), decreased dendrite length, abnormal social behavior and mechanical-induced seizures. Wildtype human DMAP1 could largely compensate for the loss of dDMAP1 in knockdown flies, whereas patient variants failed to restore or differentially rescued the phenotypes, confirming their pathogenicity with differing severity. Transcriptome profiling of dDMAP1 knockdown fly brains nominated Cbl and SF1 as downstream targets. Their overexpression rescued the aforementioned lethality and MB defects. Finally, a DNA methylation episignature was identified, leading to the molecular diagnosis of an additional patient. Our findings demonstrate that biallelic inactivating variants in DMAP1 cause a novel syndromic NDD, expanding the short list of recessive disease-causing genes within the epigenetic machinery.
Project description:Nuclear deubiquitinase BAP1 (BRCA1-Associated Protein 1) is a core component of multiprotein complexes that promote transcription by reversing the ubiquitination of histone 2A (H2A). BAP1 is a tumor suppressor gene whose germline loss-of-function variants predispose to cancer. To our knowledge, there are very rare examples of different germline variants in the same gene causing either a NDD or a tumor predisposition syndrome. Here, we report a series of 11 de novo germline heterozygous missense BAP1 variants associated with a rare syndromic neurodevelopmental disorder (NDD). Functional analysis showed that most of the variants cannot rescue the consequences of BAP1 inactivation, suggesting a loss-of-function mechanism. In T cells isolated from two affected children, H2A deubiquitination was impaired in matching peripheral blood mononuclear cells, histone H3 K27 acetylation ChIP-seq indicated that these BAP1 variants induced genome-wide chromatin state alterations, with enrichment for regulatory regions surrounding genes of the ubiquitin-proteasome system (UPS). Altogether, these results define a clinical syndrome caused by rare germline missense BAP1 variants that alter chromatin remodeling through abnormal histone ubiquitination and lead to transcriptional dysregulation of developmental genes.
Project description:Katanins are microtubule-severing ATPases. Dysfunction of katanin subunits has been implicated in impaired neurogenesis, morphogenesis, and neuronal migration. Although heterozygous variants in KATNAL2 (katanin-like 2), a known autism-spectrum disorder (ASD) risk gene, have been reported in patients with ASD or other neurodevelopmental disorders (NDD), the underlying cellular mechanisms remain incompletely defined. Whole-exome sequencing (WES) identified a homozygous missense variant in KATNAL2 (NM_001387690.1: c.1390T>C; p.(Ser464Pro)) in a pediatric patient presenting with severe global developmental delay, intellectual disability, infantile-onset epilepsy, and autistic features, extending the phenotypic spectrum beyond prior autism-focused associations. To elucidate the cellular mechanisms underlying KATNAL2 dysfunction, we established induced pluripotent stem cells (iPSCs) from patient-derived fibroblasts and differentiated them into neural progenitor cells (NPCs) for quantitative immunofluorescence analyses of microtubule organization, KATNAL2-associated microtubule regulatory network, and transcriptome profiling. In parallel, we generated a zebrafish CRISPR/Cas9 katnal2 model and assessed body patterning and axonal projections using the transgenic nbt:dsRed line. Patient iPSC-derived NPCs showed impaired interphase microtubule network organization with increased angular standard deviation in directionality and mitotic/cytokinesis abnormalities, including abnormal positioning of the microtubule-rich cytokinetic midbody region. In vivo, CRISPR/Cas9 katnal2 zebrafish crispants showed abnormal body patterning together with disorganized motor neuron and posterior lateral line nerve axonal projections. Together, these findings support KATNAL2 as a regulator of microtubule network organization and mitotic progression in human NPCs. Our data from patient-derived NPCs and zebrafish model provide functional evidence linking the p.(Ser464Pro) variant to an extended syndromic neurodevelopmental phenotype.
Project description:Genome wide DNA methylation profiling of control and neurodevelopmental disorder lymphoblastoid cell lines (LCL). The Illumina Infinium 27k Human DNA methylation Beadchip v1.2 was used to obtain DNA methylation profiles across approximately 27,000 CpGs in LCLs. Samples included 19 control, 18 Rett syndrome, 17 autism and 6 generalized epilepsy LCL samples. Six technical replicates were also included in the analysis. Bisulphite converted DNA from the 60 samples and 5 technical replicates were hybridised to the Illumina Infinium 27k Human Methylation Beadchip v1.2
Project description:Associated with dataset "A CRISPR screen in human iPSC-derived neurons reveals convergent transcriptomic effects of neurodevelopmental disorder genes"
Project description:Rare germline heterozygous missense variants of the BRCA1-Associated Protein 1 gene, BAP1, heterozygous missense variants cause a syndromic neurodevelopmental disorder
Project description:We report a new immunodeficiency disorder in mice caused by a viable hypomorphic mutation of Snrnp40, an essential gene encoding a subunit of the U5 small nuclear ribonucleoprotein (snRNP) complex of the spliceosome. Snrnp40 is ubiquitous but strongly expressed in lymphoid tissue. Homozygous mutant mice showed hypersusceptibility to infection by murine cytomegalovirus and multiple defects of lymphoid development, stability and function. Cell-intrinsic defects of hematopoietic stem cell differentiation also affected homozygous mutants. SNRNP40 deficiency in primary hematopoietic stem cells or T cells or the EL4 cell line increased the frequency of splicing errors, mostly intron retention, in several hundred messenger RNAs. Altered expression of proteins associated with immune cell function was also observed in Snrnp40-mutant cells. The immunological consequences of SNRNP40 deficiency presumably result from cumulative, moderate effects on processing of many different mRNA molecules and secondary reductions in the expression of critical immune proteins, yielding a syndromic immune disorder.