Population stratification may bias analysis of PGC-1α as a modifier of age at Huntington disease motor onset
ABSTRACT Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by motor, cognitive and behavioral disturbances, caused by the expansion of a CAG trinucleotide repeat in the HD gene. The CAG allele size is the major determinant of age at onset (AO) of motor symptoms, although the remaining variance in AO is highly heritable. The rs7665116 SNP in PPARGC1A, encoding the mitochondrial regulator PGC-1α, has been reported to be a significant modifier of AO in three European HD cohorts, perhaps due to affected cases from Italy. We attempted to replicate these findings in a large collection of (1,727) HD patient DNA samples of European origin. In the entire cohort, rs7665116 showed a significant effect in the dominant model (p value = 0.008) and the additive model (p value = 0.009). However, when examined by origin, cases of Southern European origin had an increased rs7665116 minor allele frequency (MAF), consistent with this being an ancestry-tagging SNP. The Southern European cases, despite similar mean CAG allele size, had a significantly older mean AO (p < 0.001), suggesting population-dependent phenotype stratification. When the generalized estimating equations models were adjusted for ancestry, the effect of the rs7665116 genotype on AO decreased dramatically. Our results do not support rs7665116 as a modifier of AO of motor symptoms, as we found evidence for a dramatic effect of phenotypic (AO) and genotypic (MAF) stratification among European cohorts that was not considered in previously reported association studies. A significantly older AO in Southern Europe may reflect population differences in genetic or environmental factors that warrant further investigation.
Full-textDOI: · Available from: Marina Frontali, May 16, 2015
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ABSTRACT: Peroxisome proliferator-activated receptor-gamma (PPARγ) coactivator-1 alpha (PGC-1α) is involved in the regulation of mitochondrial biogenesis, respiration, and adaptive thermogenesis. The full-length PGC-1α (FL-PGC-1α) comprises multiple functional domains interacting with several transcriptional regulatory factors such as nuclear respiratory factors, estrogen-related receptors, and PPARs; however, a number of PGC-1α splice variants have also been reported recently. In this study, we examined the expression levels of FL-PGC-1α and N-truncated PGC-1α (NT-PGC-1α), a shorter but functionally active splice variant of PGC-1α protein, in N171-82Q transgenic and 3-nitropropionic acid-induced murine model of Huntington's disease (HD). The expression levels were determined by RT-PCR in three brain areas (striatum, cortex, and cerebellum) in three age groups (8, 12, and 16 weeks). Besides recapitulating prior findings that NT-PGC-1α is preferentially increased in 16 weeks of age in transgenic HD animals, we detected age-dependent alterations in both models, including a cerebellum-predominant upregulation of both PGC-1α variants in transgenic mice, and a striatum-predominant upregulation of both PGC-1α variants after acute 3-nitropropionic acid intoxication. The possible relevance of this expression pattern is discussed. Based on our results, we assume that increased expression of PGC-1α may serve as a compensatory mechanism in response to mitochondrial damage in transgenic and toxin models of HD, which may be of therapeutic relevance.Cellular and Molecular Neurobiology 10/2014; 35(2). DOI:10.1007/s10571-014-0124-z · 2.20 Impact Factor
Article: Neues zur Huntington-KrankheitAktuelle Neurologie 09/2013; 40(07):377-392. DOI:10.1055/s-0033-1345194 · 0.32 Impact Factor
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ABSTRACT: Huntington's disease (HD) is a devastating neurodegenerative disorder that directly affects more than 1 in 10,000 persons in Western societies but, as a family disorder with a long, costly, debilitating course, it has an indirect impact on a far greater proportion of the population. Although some palliative treatments are used, no effective treatment exists for preventing clinical onset of the disorder or for delaying its inevitable progression toward premature death, approximately 15 years after diagnosis. Huntington's disease involves a movement disorder characterized by chorea, as well as a variety of psychiatric disturbances and intellectual decline, with a gradual loss of independence. A dire need exists for effective HD therapies to alleviate the suffering and costs to the individual, family, and health care system. In past decades, genetics, the study of DNA sequence variation and its consequences, provided the tools to map the HD gene to chromosome 4 and ultimately to identify its mutation as an expanded CAG trinucleotide repeat in the coding sequence of a large protein, dubbed huntingtin. Now, advances in genetic technology offer an unbiased route to the identification of genetic factors that are disease-modifying agents in human patients. Such genetic modifiers are expected to highlight processes capable of altering the course of HD and therefore to provide new, human-validated targets for traditional drug development, with the goal of developing rational treatments to delay or prevent onset of HD clinical signs. © 2014 International Parkinson and Movement Disorder SocietyMovement Disorders 09/2014; 29(11). DOI:10.1002/mds.26001 · 5.63 Impact Factor