Age-dependent progression of glomerular sclerosis in β4GalT-I−/− mice. A–D: PAM staining. β4GalT-I+/− mice at 19 weeks of age (A) and 29 weeks of age (B), and β4GalT-I−/− mice at 19 weeks of age (C) and 29 weeks of age (D). E: PAM-positive area in β4GalT-I+/− (gray circles) and β4GalT-I−/− mice (black circles) at 8 to 13, 19 to 20, 24 to 25, 28 to 30, and 44 to 48 weeks of age. The results are expressed as means ± SD. ***P < 0.001.