GNPAT and hyperinsulinemic hypoglycemia, familial, 4: Mimicking the effect of peroxisome deficiency, knockdown of the peroxisomal ether lipid synthetic enzyme glyceronephosphate-O-acyltransferase (GNPAT) (Fig. 1f, g) resulted in elongated mitochondria and decreased mtDNA (Fig. 1h, i).