Abstract
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.
Highlights
Polyacrylamidgeel electrophoresis and Southerncollagens have been suggested to play an important role in blot hybridization showed a small homozygous delethtieonassembly of pro-a chains, we previously analyzed the in the pro-a2(1) collagen gene of the patient and a corresponding region of the pro-a2(I)mRNA for the presence heterozygous pattern in both pareGntesn.omiccloning of a mutation
The procollagen trimer containsa central crograms of genomic DNA extracted from cultured skin fibroblasts of the patient, the parents, and control (GM 970 from the Human collagen domain and amino- and carboxyl-terminal propep- Genetic Mutant Cell Repository, Camden, NJ) were digested to tides which are cleaved after assembly and secretion [1]. completion with HaeIII and separated by electrophoresis on a 5%
The molecular definition of this mutationclearly shows the carboxyl-propeptide to beacritically functional domain of the procollagen molecule
Summary
Philadelphia, Pennsylvania 19104 bin (for review see Ref.20). In the latter case, numerous variants showing changes in globingene organization and expression have been extensively studied. A 580-bp HaeIII-EcoRI probe was prepared from the 1.5-kbEcoRI-EcoRIgenomic fragment which codes for part of the pro-a2(I) collagen carboxyl-propeptide [15].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
