COL4A1 and bone fragility with contractures, arterial rupture, and deafness: We found that prolyl 3 hydroxylation, which occurs infrequently, was largely unchanged by LH3 deficiency across COL1A1, COL1A2, COL3A1, COL4A1, and COL4A2 proteins and that prolyl 4 hydroxylation was reduced for COL4A1 but not for the other α chains (Fig. 4A and Table S3).