Project description:Pathogenic variants in KMT5B, a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM# 617788). Given the novelty 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 novel prominent features. 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 wildtype 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 novel pathogenic variants and clinical features in KMT5B-related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.
Project description:This analysis includes the whole-genome screening of unbalanced chromosomal rearrangements (copy-number variants; CNV) in a boy with neurodevelopmental disorders and epilepsy.
Project description:We performed a targeted NGS using the commercial gene panel design ClearSeq Inherited Disease (Agilent Technologies) to identify the pathogenic sequence variants in two boys with neurodevelopmental disorders and epilepsy and their unaffected parents
Project description:Proteins involved in transcriptional regulation harbor a demonstrated enrichment of mutations in neurodevelopmental disorders. The Sin3 (Swi-independent 3)/histone deacetylase (HDAC) complex plays a central role in histone deacetylation and transcriptional repression. Among the two vertebrate paralogs encoding the Sin3 complex, SIN3A variants cause syndromic intellectual disability, but the clinical consequences of SIN3B haploinsufficiency in humans are uncharacterized. Here, we describe a syndrome hallmarked by intellectual disability, developmental delay, and dysmorphic facial features with variably penetrant autism spectrum disorder, congenital malformations, corpus callosum defects, and impaired growth caused by disruptive SIN3B variants. Using chromosomal microarray or exome sequencing, and through international data sharing efforts, we identified nine individuals with heterozygous SIN3B deletion or single-nucleotide variants. Five individuals harbor heterozygous deletions encompassing SIN3B that reside within a ~230 kb minimal region of overlap on 19p13.11, two individuals have a rare nonsynonymous substitution, and two individuals have a single-nucleotide deletion that results in a frameshift and predicted premature termination codon. To test the relevance of SIN3B impairment to measurable aspects of the human phenotype, we disrupted the orthologous zebrafish locus by genome editing and transient suppression. The mutant and morphant larvae display altered craniofacial patterning, commissural axon defects, and reduced body length supportive of an essential role for Sin3 function in growth and patterning of anterior structures. To investigate further the molecular consequences of SIN3B variants, we quantified genome-wide enhancer and promoter activity states by using H3K27ac ChIP-seq. We show that, similar to SIN3A mutations, SIN3B disruption causes hyperacetylation of a subset of enhancers and promoters in peripheral blood mononuclear cells. Together, these data demonstrate that SIN3B haploinsufficiency leads to a hitherto unknown intellectual disability/autism syndrome, uncover a crucial role of SIN3B in the central nervous system, and define the epigenetic landscape associated with Sin3 complex impairment.
Project description:Clinical whole genome sequencing has enabled the discovery of potentially pathogenic noncoding variants in the genomes of rare disease patients with a prior history of negative genetic testing. However, interpreting the functional consequences of noncoding variants and distinguishing those that contribute to disease etiology remains a challenge. Here we address this challenge by experimentally profiling the functional consequences of rare noncoding variants detected in a cohort of undiagnosed rare disease patients at scale using a massively parallel reporter assay. We demonstrate that this approach successfully identifies rare noncoding variants that alter the regulatory capacity of genomic sequences. In addition, we describe an integrative analysis that utilizes genomic features alongside patient clinical data to further prioritize candidate variants with an increased likelihood of pathogenicity. This works represents an important step towards establishing a framework for the clinical interpretation of noncoding variants.
Project description:Functional interpretation of noncoding disease variants, which likely regulate gene expression, has been challenging. Chromatin accessibility (openness) strongly influences gene expression in neurodevelopment; however, to what extent genetic variants can alter chromatin openness in the context of brain disorders/traits is largely unknown. Using human induced pluripotent stem cell (iPSC)-derived neurons as a neurodevelopmental model, we identified abundant open-chromatin regions absent in brains and thousands of genetic variants exhibiting allele-specific open-chromatin (ASoC). ASoC variants are overrepresented in brain enhancers, transcription-factor-binding sites, and quantitative-trait-loci affecting histone modifications or DNA methylation. ASoC variants are also highly enriched for those associated with brain disorders/traits. Following-up schizophrenia-associated ASoC variants by multiplex epigenomic perturbation, computational fine-mapping, and CRISPR-editing further confirmed their regulatory activities and cis-targeted genes. Our study provides the first snapshot of neuronal ASoC landscape and a framework for prioritizing functional disease variants.
Project description:<p>Omega-3 fatty acids (n-3 polyunsaturated fatty acids; n-3 PUFAs) are essential for the functional maturation of the brain. Westernization of dietary habits in both developed and developing countries is accompanied by a progressive reduction in dietary intake of n-3 PUFAs. Low maternal intake of n-3 PUFAs has been linked to neurodevelopmental diseases in epidemiological studies, but the mechanisms by which a n-3 PUFA dietary imbalance affects CNS development are poorly understood. Active microglial engulfment of synaptic elements is an important process for normal brain development and altered synapse refinement is a hallmark of several neurodevelopmental disorders. Here, we identify a molecular mechanism for detrimental effects of low maternal n-3 PUFA intake on hippocampal development. Our results show that maternal dietary n-3 PUFA deficiency increases microglial phagocytosis of synaptic elements in the developing hippocampus, partly through the activation of 12/15- lipoxygenase (LOX)/12-HETE signaling, which alters neuronal morphology and affects cognition in the postnatal offspring. While women of child bearing age are at higher risk of dietary n-3 PUFA deficiency, these findings provide new insights into the mechanisms linking maternal nutrition to neurodevelopmental disorders.</p>
Project description:DYRK1A (dual specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 A) is a high confidence autism risk gene that encodes a conserved kinase. In addition to autism, patients with putative loss of function variants in DYRK1A exhibit microcephaly, intellectual disability, developmental delay, and congenital anomalies of the kidney and urinary tract. DYRK1A is also located within the critical region for Down syndrome; therefore, understanding the role of DYRK1A in brain development is crucial for understanding the pathobiology of multiple developmental disorders. To characterize the function of this gene, we leveraged the diploid frog, Xenopus tropicalis. We discover that Dyrk1a is expressed in ciliated tissues, localizes to ciliary axonemes and basal bodies, and is required for ciliogenesis. We also demonstrate that Dyrk1a localizes to mitotic spindles and that its inhibition leads to decreased forebrain size, abnormal cell cycle progression, and cell death during brain development. These findings provide hypotheses about potential mechanisms of pathobiology and underscore the utility of X. tropicalis as a model system for understanding neurodevelopmental disorders.
2020-06-08 | GSE149538 | GEO
Project description:Familial SYN1 pathogenic variants related Neurodevelopmental Disorders in Asian Pediatric Patients