In addition, over-expression of a GFP-tagged COA8 protein failed to induce cell death in different human cell lines (Signes et al., 2019), whereas the main biochemical hallmark of its absence was isolated mitochondrial cytochrome c oxidase (COX) deficiency (OMIM #220110). This evidence concerns the gene COA8 and hyperinsulinemic hypoglycemia, familial, 4.