One of the most recent studies showed that previously reported repression of peroxisome proliferator-activated receptor delta (PPAR-δ)—a ligand-gated transcription factor that promotes mitochondrial biogenesis and oxidative metabolism—in an HD mouse model is also found in HD patient-derived iPSC neurons (Dickey et al., 2016, 2017). The gene discussed is PPARD; the disease is Huntington disease.