Both PGC-1α and its target genes, CYCS (cytochrome c), TFAM (mitochondrial transcription factor) and NDUFS3 (NADH dehydrogenase) are reduced in the striatum of the N171-82Q HD mouse model and in human patients, in part underlying the mitochondrial dysfunction observed in HD (ref. 48). The gene discussed is CYCS; the disease is Huntington disease.