Presence of translatable mRNA for pro alpha 2(I) chains in fibroblasts from a patient with osteogenesis imperfecta whose type I collagen does not contain alpha 2(I) chains.

RNA was extracted from the cultured fibroblasts from a patient with osteogenesis imperfecta previously shown to have type I collagen lacking alpha 2(I) chains. When the RNA was examined in a cell-free translation system from reticulocytes, the translation products included both pro alpha 1(I) and pro alpha 2(I) chains. When the poly(A)-enriched polysomal RNA was examined by blot hybridization with cDNAs for pro alpha 1(I) and pro alpha 2(I) chains, mRNAs for both pro alpha 1(I) and pro alpha 2(I) were seen. The ratio of mRNAs for pro alpha 1(I) to mRNAs for pro alpha 2(I) was about the same in the patient's fibroblasts as in control fibroblasts. The results suggested that the absence of pro alpha 2(I) chains in the type I pro-collagen from this patient is probably explained by a mutation which alters the structure of pro alpha 2(I) chains and thereby prevents incorporation of the pro alpha 2(I) chains into triple-helical procollagen.