We have previously reported that the expanded polyglutamine repeats in huntingtin resulted in energetic/metabolic deficits in HD subjects as evidenced by decreased energy charge (ATP/ADP ratio) and ATP levels in human lymphoblastoid cell lines, mouse Hdh CAG knockin embryonic stem cells, and human induced pluripotent stem cells (iPSCs)/NPCs.18, 19, 20 To determine the effect of MS3 on cellular ATP levels in human NPCs HD17m8 and HD60i4, the cells were mock transfected with MS3 or GCdx. This evidence concerns the gene HTT and Huntington disease.