RESUMO
Although ribosomes are ubiquitous and essential for life, recent data indicate that monogenic causes of ribosomal dysfunction can confer a remarkable degree of specificity in terms of human disease phenotype. Box C/D small nucleolar RNAs (snoRNAs) are evolutionarily conserved non-protein-coding RNAs involved in ribosome biogenesis. Here we show that biallelic mutations in the gene SNORD118, encoding the box C/D snoRNA U8, cause the cerebral microangiopathy leukoencephalopathy with calcifications and cysts (LCC), presenting at any age from early childhood to late adulthood. These mutations affect U8 expression, processing and protein binding and thus implicate U8 as essential in cerebral vascular homeostasis.
Assuntos
Doenças de Pequenos Vasos Cerebrais/genética , Leucoencefalopatias/genética , Mutação , RNA Nucleolar Pequeno/genética , Adolescente , Adulto , Calcinose/genética , Calcinose/patologia , Linhagem Celular , Doenças de Pequenos Vasos Cerebrais/patologia , Criança , Pré-Escolar , Cromossomos Humanos Par 17 , Estudos de Coortes , Cistos/genética , Cistos/patologia , Exoma , Feminino , Ligação Genética , Genoma Humano , Humanos , Lactente , Leucoencefalopatias/patologia , Masculino , Pessoa de Meia-Idade , Análise de Sequência de DNA , Adulto JovemRESUMO
Coats plus is a highly pleiotropic disorder particularly affecting the eye, brain, bone and gastrointestinal tract. Here, we show that Coats plus results from mutations in CTC1, encoding conserved telomere maintenance component 1, a member of the mammalian homolog of the yeast heterotrimeric CST telomeric capping complex. Consistent with the observation of shortened telomeres in an Arabidopsis CTC1 mutant and the phenotypic overlap of Coats plus with the telomeric maintenance disorders comprising dyskeratosis congenita, we observed shortened telomeres in three individuals with Coats plus and an increase in spontaneous γH2AX-positive cells in cell lines derived from two affected individuals. CTC1 is also a subunit of the α-accessory factor (AAF) complex, stimulating the activity of DNA polymerase-α primase, the only enzyme known to initiate DNA replication in eukaryotic cells. Thus, CTC1 may have a function in DNA metabolism that is necessary for but not specific to telomeric integrity.
Assuntos
Anormalidades Múltiplas/genética , Predisposição Genética para Doença/genética , Telangiectasia Retiniana/genética , Proteínas de Ligação a Telômeros/genética , Telômero/patologia , Sequência de Bases , Citometria de Fluxo , Histonas/metabolismo , Dados de Sequência Molecular , Telangiectasia Retiniana/patologia , Análise de Sequência de DNA/métodosRESUMO
Alexander disease is a rare neurodegenerative leucoencephalopathy caused by de novo mutations in the GFAP gene. Infantile, juvenile, and adult subtypes have been described and the clinical and radiological phenotypes are broad. Here we report on a single case of juvenile-onset Alexander disease associated with a novel frameshift mutation in the GFAP gene. The 8-year-old male patient had a relatively mild clinical phenotype characterized by dystonia, intermittent episodes of raised intracranial pressure, and characteristic radiological changes. He also presented with the additional and to our knowledge previously unreported, neuroimaging finding of periventricular calcification. We postulate that in children with leucoencephalopathy and periventricular calcification of undetermined aetiology, the diagnosis of Alexander disease should be considered. If the magnetic resonance imaging findings are compatible with Alexander disease, then DNA analysis of the GFAP gene should be performed even if the full criteria for a neuroradiological diagnosis are not met.
