However, in demonstrating that CL modulation can in part rescue CI defects, we propose CI assembly, assembly factor expression (NDUFAF1), and subunit expression (MT-ND3, NDUFA5, NDUFAB1, NDUFB2, and NDUFB4) are valid cellular markers for treatment efficacy in BTHS. The gene discussed is NDUFB4; the disease is Barth syndrome.