Premium
Splice site mutation causing deletion of exon 21 sequences from the proα2(I) chain of type I collagen in a patient with severe dentinogenesis imperfecta but very mild osteogenesis imperfecta
Author(s) -
Nicholls Alan C.,
Oliver Jane,
McCarron Seamus,
Winter Gerald B.,
Pope F. Michael
Publication year - 1996
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/(sici)1098-1004(1996)7:3<219::aid-humu6>3.0.co;2-5
Subject(s) - dentinogenesis imperfecta , osteogenesis imperfecta , exon , biology , mutation , splice , genetics , splice site mutation , type i collagen , bioinformatics , gene , anatomy , alternative splicing , endocrinology
An eight‐year‐old boy was referred for dental assessment of dentinogenesis imperfecta, a full clinical examination also revealed joint hypermobility and some features of mild osteogenesis imperfecta although he had suffered few fractures. Analysis of the collagens produced by both gingival and skin fibroblast cultures showed the synthesis and intracellular retention of an abnormal α2(I) chain that migrated faster than normal on SDS‐PAGE. Cyanogen bromide peptide mapping of this intracellular protein indicated a probable deletion in the N‐terminal peptide α2CB4. The denaturation temperature of the mutant protein was only 36°C, some 6°C below normal. At 37°C secretion of abnormal protein was not detectable but at a lower temperature (30°C) some was secreted into the medium. RT‐PCR amplification of mRNA coding for α2CB4 revealed a heterozygous deletion of the 108 bp exon 21 of COL1A2. Sequencing of PCR amplified genomic DNA identified a C→A transition in the moderately conserved + 5 position of the IVS 21 5′ consensus splice site causing the skipping of exon 21. Hybridization with allele‐specific oligonucleotides showed no other family member had this base change. Since the cDNA deletion was associated with the (−) allele of a Pvu II polymorphism in exon 25 of COL1A2 we could demonstrate that the mutant pre‐mRNA was alternatively spliced yielding both full length and deleted transcripts. Family genotype analysis indicated the mutation had originated in the paternal α2(I) gene. © 1996 Wiley‐Liss, Inc.