The first of these cell lines was derived from Patient N (Pat.N) who had an isolated CIII deficiency due to a cytochrome c1 (CYC1) mutation [48,49], impairing the assembly of CIII (Figure 3A, Lane N, UQCRC1 panel). Here, CYC1 is linked to hyperinsulinemic hypoglycemia, familial, 4.