Osteogenesis imperfecta: cloning of a pro-alpha 2(I) collagen gene with a frameshift mutation.
Osteogenesis imperfecta (OI), a brittle-bone disorder, constitutes a major group of the inherited diseases of connective tissue. We have been studying an autosomal recessive form of OI in which the severely affected patient has inherited two abnormal pro-alpha 2(I) collagen alleles from consanguinous parents. Previously, nuclease S1 mapping was employed to localize a defect in the mRNA coding for the pro-alpha 2(I) collagen carboxyl-propeptide. The mutation prevents incorporation of pro-alpha 2(I) chains into the normal type I procollagen heterotrimer resulting in secretion of only pro-alpha 1(I) homotrimers. Here we report complete characterization of the corresponding region of the altered gene. Polyacrylamide gel electrophoresis and Southern blot hybridization showed a small homozygous deletion in the pro-alpha 2(I) collagen gene of the patient and a heterozygous pattern in both parents. Genomic cloning of the patient's DNA revealed a four nucleotide frameshift deletion in exon 1 near the end of translation which apparently instigates use of a new termination codon four nucleotides 3' to the original site. The mutation identified in this OI patient directly demonstrates the critical role of the carboxyl-propeptides in chain selection and assembly during the biosynthesis of procollagen.
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005260:Female; D005796:Genes; D006801:Humans; D008297:Male; D009154:Mutation; D009693:Nucleic Acid Hybridization; D010013:Osteogenesis Imperfecta / Q000235:genetics* / Q000378:metabolism; D010375:Pedigree; D011347:Procollagen / Q000235:genetics*
D011347:Procollagen; D004262:DNA Restriction Enzymes