PPARGC1A and Huntington disease: Weydt et al. [50], in a study involving 447 unrelated HD patients, showed an association between two haplotypes in the PPARG coactivator 1 alpha gene (PPARGC1A or PGC-1alpha, chromosome 4p15.2, Gene ID 10891, MIM 604517; this gene encodes a transcriptional coactivator that regulates the genes involved in energy metabolism) and the age at the onset of HD.