Project description:CDAGS Syndrome is a rare congenital disorder characterized by Craniosynostosis, Delayed closure of the fontanelles, cranial defects, clavicular hypoplasia, Anal and Genitourinary malformations, and Skin manifestations. We performed exome sequencing to identify the underlying molecular cause in five patients with CDAGS syndrome from four distinct families. Whole exome sequencing revealed rare variants that disrupt highly conserved nucleotides within the RNU12 gene. RNU12 encodes a small nuclear RNA that is a component of the minor spliceosome and is essential for minor intron splicing. Targeted sequencing confirmed allele segregation within the four families. All five patients in this cohort have a rare variant on one allele that either disrupts the secondary structure or the Sm binding site of the RNU12 snRNA. The variant on the other allele, shared among all five cases, alters a highly conserved nucleotide within the precursor U12 snRNA 3’ extension that is absent in 1440 unrelated healthy controls. All of the variants are either rare or absent from all searched public databases. Whole transcriptome sequencing analysis identified gene dysregulation and specific defects in intron retention in a subset of minor intron splicing. These findings provide evidence of the involvement of RNU12 in craniosynostosis, anal and genitourinary patterning and cutaneous disease.
Project description:Alterations in RNA-splicing are a molecular hallmark of several neurological diseases, including muscular dystrophies where mutations in genes involved in RNA metabolism or characterised by alterations in RNA splicing have been described. Here, we present five patients from two unrelated families with a limb-girdle muscular dystrophy (LGMD) phenotype carrying a biallelic variant in SNUPN gene. Snurportin-1, the protein encoded by SNUPN, plays an important role in the nuclear transport of small nuclear ribonucleoproteins (snRNPs), essential components of the spliceosome. We combine deep phenotyping, including clinical features, histopathology and muscle magnetic resonance image (MRI), with functional studies in patient-derived cells and muscle biopsies to demonstrate that variants in SNUPN are the cause of a new type of LGMD according to current definition. Moreover, an in vivo model in Drosophila melanogaster further supports the relevance of Snurportin-1 in muscle. SNUPN patients show a similar phenotype characterised by proximal weakness starting in childhood, restrictive respiratory dysfunction and prominent contractures, although interindividual variability in terms of severity even in individuals from the same family was found. Muscle biopsy showed myofibrillar-like features consisting of myotilin deposits and Z-disc disorganisation. MRI showed predominant impairment of paravertebral, vasti, sartorius, gracilis, peroneal and medial gastrocnemius muscles. Conservation and structural analyses of Snurportin-1 p.Ile309Ser variant suggest an effect in nuclear-cytosol snRNP trafficking. In patient-derived fibroblasts and muscle, cytoplasmic accumulation of snRNP components is observed, while total expression of Snurportin-1 and snRNPs remains unchanged, which demonstrates a functional impact of SNUPN variant in snRNP metabolism. Furthermore, RNA-splicing analysis in patients’ muscle showed widespread splicing deregulation, in particular in genes relevant for muscle development and splicing factors that participate in the early steps of spliceosome assembly. In conclusion, we report that SNUPN variants are a new cause of limb girdle muscular dystrophy with specific clinical, histopathological and imaging features, supporting SNUPN as a new gene to be included in genetic testing of myopathies. These results further support the relevance of splicing-related proteins in muscle disorders.
Project description:We aimed to define a novel autosomal recessive neurodevelopmental disorder, characterize its clinical features, and identify the underlying genetic cause for this condition. Clinical and genetic data from affected individuals with neurological disorders were matched across families from five global sites. Here, we report five recessive CSPG4 (NM_001897) missense variants [three homozygous: c.A1370G (p.Asp457Gly), c.2627G>A (p.Arg876His) and c.3247C>A (p.Gln1083Lys), and two compound heterozygote: c.A1370G and c.5156A>G (p.Asp457Gly and p.Gln1719Arg) and c.658A>G and c.1220_1221delinsTG (p.(Thr220Ala and p.Pro407Leu)] by next-generation sequencing of five unrelated families with seven affected subjects. All subjects share a novel neurodevelopmental syndrome characterized by severe intellectual disability, global developmental delay, delayed ability to walk, speech and language delay, distinctive facial features, along with varying degrees of neurological impairment, including hypotonia, cerebellar hypoplasia, and/or seizures. All CSPG4 variants were predicted to be damaging using in silico tools, and three-dimensional molecular modeling suggested significant alterations in protein stability, compromising inter- and intra-molecular interactions. The impact on neurological and craniofacial development was analyzed in CRISPR/Cas9-mediated zebrafish models. CSPG4 variants affected notochord development, neuronal function, and cerebellar structure along with a disorganized head scaffold with anomalous skeletal and cartilage components. Two individuals metabolomics and crispant transcriptomics revealed significant perturbation of metabolites, extracellular matrix (ECM) regulating pathways, and genes previously described to cause mental retardation, dwarfism, and facial anomalies in humans. Our study links novel, rare, damaging variants of the ECM gene CSPG4 to a novel recessive Mendelian neurodevelopmental disorder in humans and supports the role of CSPG4 in early development.
Project description:PNPLA8, one of the calcium-independent phospholipase A2 enzymes, is involved in various physiological conditions through the maintenance of membrane phospholipids. However, little is known about its role in brain development. Here, we report 14 individuals from 12 unrelated families with biallelic ultra-rare variants in PNPLA8 presenting with a wide spectrum of clinical features ranging from developmental and epileptic-dyskinetic encephalopathy (DEDE) to progressive movement disorders and no phenotype depending on the variants and their positions. Complete loss of PNPLA8 was associated with the severe end of the spectrum showing DEDE manifestations and congenital or progressive microcephaly. Using cerebral organoids generated from human induced pluripotent stem cells (iPSCs), we found that loss of PNPLA8 reduces the abundance of basal radial glial cells (bRGCs) and upper-layer neurons. By spatial transcriptomic analysis targeting apical radial glial cells (aRGCs), we found the downregulation of bRGC-related gene sets in patient-derived cerebral organoids. Lipidomic analysis revealed a decrease in the amount of lysophosphatidic acid, lysophosphatidylethanolamine, and phosphatidic acid, indicative of the disturbed phospholipid metabolism in PNPLA8 knockout neural progenitor cells. Our data suggest that PNPLA8 has a critical role in the bRGC-mediated expansion of the developing human cortex by regulating the fate commitment of aRGCs.
Project description:PNPLA8, one of the calcium-independent phospholipase A2 enzymes, is involved in various physiological conditions through the maintenance of membrane phospholipids. However, little is known about its role in brain development. Here, we report 14 individuals from 12 unrelated families with biallelic ultra-rare variants in PNPLA8 presenting with a wide spectrum of clinical features ranging from developmental and epileptic-dyskinetic encephalopathy (DEDE) to progressive movement disorders and no phenotype depending on the variants and their positions. Complete loss of PNPLA8 was associated with the severe end of the spectrum showing DEDE manifestations and congenital or progressive microcephaly. Using cerebral organoids generated from human induced pluripotent stem cells (iPSCs), we found that loss of PNPLA8 reduces the abundance of basal radial glial cells (bRGCs) and upper-layer neurons. By spatial transcriptomic analysis targeting apical radial glial cells (aRGCs), we found the downregulation of bRGC-related gene sets in patient-derived cerebral organoids. Lipidomic analysis revealed a decrease in the amount of lysophosphatidic acid, lysophosphatidylethanolamine, and phosphatidic acid, indicative of the disturbed phospholipid metabolism in PNPLA8 knockout neural progenitor cells. Our data suggest that PNPLA8 has a critical role in the bRGC-mediated expansion of the developing human cortex by regulating the fate commitment of aRGCs.ナカセンセイキニュウ
Project description:Heterozygous pathogenic variants in POLR1A were identified as the cause of Acrofacial Dysostosis, Cincinnati-type in 2015. Craniofacial anomalies reminiscent of Treacher Collins syndrome were the predominant phenotype observed in the first 3 affected individuals. We have subsequently identified 17 additional individuals with 12 unique (11 novel) heterozygous variants in POLR1A and observed numerous additional phenotypes including developmental delay, infantile spasms, and structural cardiac defects. To understand the pathogenesis of this pleiotropy, we created an allelic series of POLR1A using a combination of in vivo (mouse) and in vitro models. We describe distinct spatiotemporal requirements for Polr1a during mouse embryogenesis and identify a requirement for Polr1a for survival of pre migratory and migratory neural crest cells, forebrain precursors, and the second heart field. We used CRISPR/Cas9 to recapitulate two human alleles in mouse, demonstrating pathogenicity of one and likely benign nature of the other. Our work greatly expands the phenotype of human POLR1A-related disorders, provides new evidence of reduced penetrance and variable expression of POLR1A heterozygous variants, and demonstrates a multi-faceted approach to characterize and define pathogenicity of variants.