genase [ubiquinone] 1 alpha subcomplex assembly factor 4(NDUFAF4) is involved in the compilation of mitochondrial NADH: ubiquinone oxidoreductase complex(complex I). In addition, NDUFAF4 is involved in cell proliferation and survival of hormone-dependent tumor cells. NDUFAF4 may also be a regulator of breast tumor cell invasion. NDUFAF4 gene mutations cause the mitochondrial complex I deficiency.