arise from defects in oxidative phosphorylation (OXPHOS). Their complex mode of inheritance and diverse clinical presentations render the diagnosis of MDs challenging and, to date, most lack a cure. Here, we build on previous efforts to discover genes necessary for OXPHOS and report a highly complementary galactose-sensitized CRISPR-Cas9 “growth” screen, presenting an updated inventory now with 481 OXPHOS genes, including 157 linked to MDs. We further focus on FAM136A, a gene associated with Ménière’s disease and show that it supports inter-membrane space protein homeostasis and OXPHOS in cell lines, mice, and patients. Our study identifies a mitochondrial basis in a familial form of Ménière’s disease (fMD), provides a comprehensive resource of OXPHOS-related genes, and sheds light on the pathways involved in mitochondrial disorders, with the potential to guide future diagnostics and treatments for MDs.