Project description:Recessive mutations in EXOSC3, encoding a subunit of the human RNA exosome complex, cause Pontocerebellar hypoplasia type 1b (PCH1B). We report a boy with severe muscular hypotonia, psychomotor retardation, progressive microcephaly, and cerebellar atrophy. Biochemical abnormalities comprised mitochondrial Complex I and PDHc deficiency. Whole exome sequencing uncovered a known EXOSC3-mutation p.(D132A) as the underlying cause. In patient fibroblasts, >50% of the EXOSC3 protein was trapped in the cytosol. mtDNA-copy numbers in muscle were reduced to 40%, but mutations in the mtDNA and nuclear mitochondrial genes were excluded. RNA-seq of patient muscle showed highly increased mRNA-copy numbers, especially for genes encoding structural subunits of OXPHOS-complexes I, III, and IV, possibly due to reduced degradation by a dysfunctional exosome complex. This is the first case of mitochondrial dysfunction associated with an EXOSC3 mutation, which expands the phenotypic spectrum of PCH1B. We discuss the links between exosome and mitochondrial dysfunction.
Project description:Pontocerebellar Hypoplasia Type 10 (PCH10) is a childhood neurodegenerative disease caused by bi-allelic p.R140H variants in CLP1, a multifunctional RNA kinase, by unknown pathophysiological mechanisms. Here, we combine novel patient data with mutation-specific in vivo and in vitro models to define motor neuron dysfunction as a penetrant, prominent feature of PCH10 and uncover a previously unrecognized mRNA misprocessing signature in motor neurons that likely contributes to pathology.
Project description:Pontocerebellar Hypoplasia Type 10 (PCH10) is a childhood neurodegenerative disease caused by bi-allelic p.R140H variants in CLP1, a multifunctional RNA kinase, by unknown pathophysiological mechanisms. Here, we combine novel patient data with mutation-specific in vivo and in vitro models to define motor neuron dysfunction as a penetrant, prominent feature of PCH10 and uncover a previously unrecognized mRNA misprocessing signature in motor neurons that likely contributes to pathology.
Project description:Pontocerebellar Hypoplasia Type 10 (PCH10) is a childhood neurodegenerative disease caused by bi-allelic p.R140H variants in CLP1, a multifunctional RNA kinase, by unknown pathophysiological mechanisms. Here, we combine novel patient data with mutation-specific in vivo and in vitro models to define motor neuron dysfunction as a penetrant, prominent feature of PCH10 and uncover a previously unrecognized mRNA misprocessing signature in motor neurons that likely contributes to pathology.
Project description:Extracellular vesicles (EVs) enable cell-to-cell communication in the nervous system essential for development and adult function. Endosomal Sorting Complex Required for Transport (ESCRT) complex proteins regulate EV formation and release. Recent work shows loss of function (LOF) mutations in, CHMP1A, which encodes one ESCRT-III member, cause autosomal recessive microcephaly with pontocerebellar hypoplasia in humans (Mochida et al., 2012). Here we show CHMP1A is required for maintenance of progenitors in human cerebral organoids and that mouse Chmp1a is required for progenitor proliferation in cortex and cerebellum and specifically for sonic hedgehog (SHH) mediated proliferation through SHH secretion. CHMP1A mutation reduces intraluminal vesicle (ILV) formation in multivesicular bodies (MVBs), and EV release. SHH protein is present on a subset of EVs marked by a unique set of proteins we call ART-EVs. CHMP1A’s requirement in formation of ART-EVs and other EVs provides a model to elucidate EV functions in multiple brain processes.