Restriction fragment length polymorphism associated with the pro alpha 2(I) gene of human type I procollagen. Application to a family with an autosomal dominant form of osteogenesis imperfecta.

Abstract

A B S T R A C T One cloned complementary DNA and one genomnic subclone were used to detect restriction fragment length polymorphism associated with the proa2(I) gene for human type I procollagen. The restriction fragments obtained from examination of 30-122 chromosomes confirmed previous indications that the proa2(I) gene is found in a single copy in the human haploid genome. One highly polymorphic site was detected with EcoRI in the 5'-half of the gene. The restriction site polymorphism at the site had an allelic frequency of 0.38, and it generated two fragments of 10.5 and 3.5 kilobase in homozygous individuals. The restriction fragment length polymorphism generated at the EcoRI site was used to study affected and nonaffected individuals in four generations of a family with an autosomal dominant form of osteogenesis imperfecta. The data demonstrated a linkage of the phenotype to a proa2(I) allele with a lod score of 2.41 at a recombination fraction (0) of 0. The data therefore provided presumptive evidence that osteogenesis imperfecta in this family is caused by a mutation in the proa2(I) gene or some contiguous region of the genome. The relatively high frequency of polymorphism at the EcoRI site makes it useful for studying a broad range of genetic disorders in which mutations in type I procollagen are suspected. In addition, the polymorphic site should provide useful markers for linkage

Osteogenesis imperfecta type IV. Biochemical confirmation of genetic linkage to the pro alpha 2(I) gene of type I collagen.

“…This approach enabled us to focus attention on only one class of constituent chains of type I collagen. In this report we describe studies of type I collagen synthesized by cells cultured from one unaffected and two affected members of this pedigree (26). The affected members are heterozygous for a mutation in the proa2(I) gene that produces a shortened proa2(I) chain, thus confirming linkage in this family.…”

“…Thus, the slower migrating population of al(I) was overmodified amino-terminal to the a l(I)CB7 domain. These findings contained an apparent paradox: although the genetic linkage data (26) indicated that the mutation should be in an a2(I) chain, the evident structural abnormality in type I collagen was overmodification of the amino-terminal half of some intracellular al(I) chains produced by the OI cells. Because Steinmann et al (12) have demonstrated that a mutation of a 1(I) could cause overmodification in all three constituent achains in a molecule at residues amino-terminal to the mutation, we hypothesized that a mutation in the middle ofan a2(I) chain might also cause excessive posttranslational modification aminoterminal to its location in all chains in such a molecule but that because a2(I) normally is more modified than a 1(I), overmodification in a2(I) might be more difficult to detect.…”

“…Individuals with 01 type IV have normal or gray rather than blue sclerae, may have mild to moderate short stature with long bone deformity, and have a far greater incidence of dentinogenesis imperfecta (23,24). We have recently provided evidence of abnormal triple helical structure of type I collagen in one patient with the 01 type IV phenotype (25), and Tsipouras et al have demonstrated linkage of the OI type IV phenotype to the proa2(I) gene of type I collagen on chromosome 7 in four pedigrees (26)(27)(28).…”

“…as type I collagen, we chose to study cell strains from individuals in a large pedigree in which there is evidence of linkage of the 01 type IV phenotype to the proa2(I) gene (26). This approach enabled us to focus attention on only one class of constituent chains of type I collagen.…”

Length polymorphisms in new human collagen‐like loci

“…The fragments at Sites 1 and 2 are detected with a pro-~2(I) eDNA probe, but the restriction map of the COL1A2 gene does not contain the 7.4 kb HindlII and 3.0 kb PstI fragments characteristic of Site I nor the 4.6 kb HindllI and 5.2 kb PstI fragments characteristic of Site 2 [15,16,17]. COL1A2 genomic clones that span the same region of the gene as does the eDNA were used to probe samples where the eDNA probe had detected length polymorphisms at Sites 1 or 2 (Fig.…”