RESUMO
Familial combined hyperlipidemia (FCHL, MIM-144250) is a common, multifactorial and heterogeneous dyslipidemia predisposing to premature coronary artery disease and characterized by elevated plasma triglycerides, cholesterol, or both. We identified a mutant mouse strain, HcB-19/Dem (HcB-19), that shares features with FCHL, including hypertriglyceridemia, hypercholesterolemia, elevated plasma apolipoprotein B and increased secretion of triglyceride-rich lipoproteins. The hyperlipidemia results from spontaneous mutation at a locus, Hyplip1, on distal mouse chromosome 3 in a region syntenic with a 1q21-q23 FCHL locus identified in Finnish, German, Chinese and US families. We fine-mapped Hyplip1 to roughly 160 kb, constructed a BAC contig and sequenced overlapping BACs to identify 13 candidate genes. We found substantially decreased mRNA expression for thioredoxin interacting protein (Txnip). Sequencing of the critical region revealed a Txnip nonsense mutation in HcB-19 that is absent in its normolipidemic parental strains. Txnip encodes a cytoplasmic protein that binds and inhibits thioredoxin, a major regulator of cellular redox state. The mutant mice have decreased CO2 production but increased ketone body synthesis, suggesting that altered redox status down-regulates the citric-acid cycle, sparing fatty acids for triglyceride and ketone body production. These results reveal a new pathway of potential clinical significance that contributes to plasma lipid metabolism.
Assuntos
Proteínas de Transporte/genética , Clonagem Molecular , Hiperlipidemia Familiar Combinada/genética , Animais , Animais Congênicos , Dióxido de Carbono/metabolismo , Proteínas de Transporte/metabolismo , Cromossomos Artificiais Bacterianos/genética , Cromossomos Humanos Par 1/genética , Ciclo do Ácido Cítrico/genética , Códon/genética , Códon sem Sentido , Mapeamento de Sequências Contíguas , Cosmídeos/genética , Cricetinae , Cruzamentos Genéticos , Modelos Animais de Doenças , Metabolismo Energético/genética , Éxons/genética , Ácidos Graxos/metabolismo , Haplótipos/genética , Humanos , Células Híbridas , Hiperlipidemia Familiar Combinada/metabolismo , Corpos Cetônicos/biossíntese , Camundongos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Oxirredução , Tiorredoxinas/antagonistas & inibidores , Triglicerídeos/sangueRESUMO
Genetic association of ABCA1 or the ATP-binding cassette A1 transporter with late-onset Alzheimer's disease (LOAD) has recently been proposed for a haplotype comprised of three single nucleotide polymorphisms (SNPs). We have genotyped these and other ABCA1 SNPs in a LOAD case-control series of 796 individuals (419 cases versus 377 controls) collected at Washington University. While our sample series is larger and thus presumably has greater power than any of the series used to implicate ABCA1, we were unable to replicate the published association, using either single markers or multiple marker haplotypes. Further, we did not observe significant and replicated association of other ABCA1 SNPs we examined with the disease, thus these ABCA1 variants do not appear to influence the risk of LOAD in this study.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Doença de Alzheimer/genética , Transportador 1 de Cassete de Ligação de ATP , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Feminino , Humanos , Desequilíbrio de Ligação , Masculino , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/biossíntese , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodosRESUMO
Knudson's two-hit hypothesis postulates that genetic alterations in both alleles are required for the inactivation of tumor-suppressor genes. Genetic alterations include small or large deletions and mutations. Over the past years, it has become clear that epigenetic alterations such as DNA methylation are additional mechanisms for gene silencing. Restriction Landmark Genomic Scanning (RLGS) is a two-dimensional gel electrophoresis that assesses the methylation status of thousands of CpG islands. RLGS has been applied successfully to scan cancer genomes for aberrant DNA methylation patterns. So far, the majority of this work was done using NotI as the restriction landmark site. Here, we describe the development of RLGS using AscI as the restriction landmark site for genome-wide scans of cancer genomes. The availability of AscI as a restriction landmark for RLGS allows for scanning almost twice as many CpG islands in the human genome compared with using NotI only. We describe the development of an AscI-EcoRV boundary library that supports the cloning of novel methylated genes. Feasibility of this system is shown in three tumor types, medulloblastomas, lung cancers, and head and neck cancers. We report the cloning of 178 AscI RLGS fragments via two methods by use of this library.
Assuntos
Ilhas de CpG/genética , Metilação de DNA , Desoxirribonucleases de Sítio Específico do Tipo II , Biblioteca Gênica , Genoma Humano , Clonagem Molecular , Fragmentação do DNA/genética , Eletroforese em Gel Bidimensional/métodos , Regulação Neoplásica da Expressão Gênica/genética , Genes Neoplásicos/genética , Humanos , Mapeamento por RestriçãoRESUMO
Although several genes have been implicated in the development of the early-onset autosomal dominant form of Alzheimer's disease (AD), the genetics of late-onset AD (LOAD) is complex. Loci on several chromosomes have been linked to the disease, but so far only the apolipoprotein E gene has been consistently shown to be a risk factor. We have performed a large-scale single-nucleotide polymorphism (SNP)-based association study, across the region of linkage on chromosome 12, in multiple case-control series totaling 1,089 LOAD patients and 1,196 control subjects and report association with SNPs in the glyceraldehyde-3-phosphate dehydrogenase (GAPD) gene. Subsequent analysis of GAPD paralogs on other chromosomes demonstrated association with two other paralogs. A significant association between LOAD and a compound genotype of the three GAPD genes was observed in all three sample sets. Individually, these SNPs make differential contributions to disease risk in each of the casecontrol series, suggesting that variants in functionally similar genes may account for series-to-series heterogeneity of disease risk. Our observations raise the possibility that GAPD genes are AD risk factors, a hypothesis that is consistent with the role of GAPD in neuronal apoptosis.