RESUMO
ATRX is an X-linked gene of the SWI/SNF family, mutations in which cause syndromal mental retardation and downregulation of α-globin expression. Here we show that ATRX binds to tandem repeat (TR) sequences in both telomeres and euchromatin. Genes associated with these TRs can be dysregulated when ATRX is mutated, and the change in expression is determined by the size of the TR, producing skewed allelic expression. This reveals the characteristics of the affected genes, explains the variable phenotypes seen with identical ATRX mutations, and illustrates a new mechanism underlying variable penetrance. Many of the TRs are G rich and predicted to form non-B DNA structures (including G-quadruplex) in vivo. We show that ATRX binds G-quadruplex structures in vitro, suggesting a mechanism by which ATRX may play a role in various nuclear processes and how this is perturbed when ATRX is mutated.
Assuntos
DNA Helicases/metabolismo , Proteínas Nucleares/metabolismo , Animais , Células Cultivadas , Imunoprecipitação da Cromatina , Cromossomos de Mamíferos/metabolismo , Ilhas de CpG , DNA Helicases/genética , DNA Ribossômico/metabolismo , Quadruplex G , Expressão Gênica , Estudo de Associação Genômica Ampla , Histonas/metabolismo , Humanos , Camundongos , Repetições Minissatélites , Mutação , Proteínas Nucleares/genética , Telômero/metabolismo , Proteína Nuclear Ligada ao XRESUMO
Autism is a highly heritable neurodevelopmental disorder whose underlying genetic causes have yet to be identified. To date, there have been eight genome screens for autism, two of which identified a putative susceptibility locus on chromosome 16p. In the present study, 10 positional candidate genes that map to 16p11-13 were examined for coding variants: A2BP1, ABAT, BFAR, CREBBP, EMP2, GRIN2A, MRTF-B, SSTR5, TBX6, and UBN1. Screening of all coding and regulatory regions by denaturing high-performance liquid chromatography identified seven nonsynonymous changes. Five of these mutations were found to cosegregate with autism, but the mutations are not predicted to have deleterious effects on protein structure and are unlikely to represent significant etiological variants. Selected variants from candidate genes were genotyped in the entire International Molecular Genetics Study of Autism Consortium collection of 239 multiplex families and were tested for association with autism by use of the pedigree disequilibrium test. Additionally, genotype frequencies were compared between 239 unrelated affected individuals and 192 controls. Patterns of linkage disequilibrium were investigated, and the transmission of haplotypes across candidate genes was tested for association. Evidence of single-marker association was found for variants in ABAT, CREBBP, and GRIN2A. Within these genes, 12 single-nucleotide polymorphisms (SNPs) were subsequently genotyped in 91 autism trios (one affected individual and two unaffected parents), and the association was replicated within GRIN2A (Fisher's exact test, P<.0001). Logistic regression analysis of SNP data across GRIN2A and ABAT showed a trend toward haplotypic differences between cases and controls.
Assuntos
4-Aminobutirato Transaminase/genética , Transtorno Autístico/genética , Cromossomos Humanos Par 16 , Predisposição Genética para Doença , Testes Genéticos , Subunidades Proteicas/genética , Receptores de N-Metil-D-Aspartato/genética , Alelos , Mapeamento Cromossômico , Frequência do Gene , Marcadores Genéticos , Variação Genética , Haplótipos , Humanos , Desequilíbrio de Ligação , Modelos Logísticos , Mutação de Sentido Incorreto , Linhagem , Polimorfismo de Nucleotídeo Único , Análise de RegressãoRESUMO
Ankylosing spondylitis (AS) is a common and highly heritable inflammatory arthropathy. Although the gene HLA-B27 is almost essential for the inheritance of the condition, it alone is not sufficient to explain the pattern of familial recurrence of the disease. We have previously demonstrated suggestive linkage of AS to chromosome 2q13, a region containing the interleukin 1 (IL-1) family gene cluster, which includes several strong candidates for involvement in the disease. In the current study, we describe strong association and transmission of IL-1 family gene cluster single-nucleotide polymorphisms and haplotypes with AS.