Retroviral overexpression of wild-type B4GalT5 cDNA in TAL-B4G5#2 restored Stx sensitivity and glycolipid composition in the cells, which confirmed that the deleted mutation of B4GalT5 is the cause of glycolipid deficiency in TAL-B4G5#2 (Figures 6E, S5D and E). Here, B4GALT5 is linked to hyperinsulinemic hypoglycemia, familial, 4.