Singhal et al. previously reported 46 proteins that were differentially expressed by at least 2-fold or higher in patient-derived fibroblasts of healthy patients versus Niemann-Pick disease type C1 patients (NPC1 mutant).29 We found that 40 of these 46 proteins co-immunoprecipitated with NDUFA4L2 to a greater extent in RCC4-P cells versus RCC4-KO-643 cells (Table 1), suggesting that NDUFA4L2 is associated with NPC1 and further supporting the location of NDUFA4L2 in the early lysosomes. The gene discussed is SLC49A4; the disease is Niemann-Pick disease, type C1.