Identification of a mutation that causes exon skipping during collagen pre-mRNA splicing in an Ehlers-Danlos syndrome variant

D. Weil, M. Bernard, N. Combates, M. K. Wirtz, D. W. Hollister, B. Steinmann, F. Ramirez

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Abstract

Recent biochemical studies have shown that the fibroblasts from a patient with Ehlers-Danlos Syndrome Type VIIB produce nearly equal amounts of normal and shortened pro-α2(I) collagen chains (Wirtz., M.K., Glanville, R.W., Steinmann, B., Rao, V.H., and Hollister, D. (1987) J. Biol. Chem. 262, 16376-16385). Compositional and sequencing studies of the abnormal pro-α2(I) chain identified an interstitial deletion of 18 residues corresponding to the N-telopeptide of the collagen molecule. Since this region is encoded by a 54-base pair exon, number 6, the protein defect could have been caused by gene deletion, abnormal pre-mRNA splicing, or both. Here, in order to elucidate the molecular nature of this mutation we have analyzed the sequences of pro-α2(I) collagen cDNA and genomic clones obtained from RNA and DNA of the patient's fibroblasts. Using oligomer-specific cloning we identified a cDNA that contains a 54-base pair deletion corresponding precisely to the sequence of exon 6. Identification of the normal gene was based on the finding of an identical sequence polymorphism in a normal cDNA and in the genomic clone derived from one of the two collagen alleles. The other gene, instead, displayed a base substitution (T to C) in the obligatory GT dinucleotide of the 5' splice-site sequence of intron 6. Analysis of nearly 100 base pairs immediately 5' to exons 5, 6, and 7, and 3' to exons 5 and 7 did not reveal any additional change. Therefore, the data strongly suggest that the observed GT-to-GC transition at the splice donor site of intron 6 generates an abnormally spliced mRNA in which the sequence of exon 5 is joined to the sequence of exon 7. Since skipping of exon 6 does not interfere with the coding frame of the mRNA, the resulting shortened polypeptide, albeit utilized in the assembly of a procollagen trimer, ultimately causes the Ehlers-Danlos Syndrome Type VII phenotype.

Original languageEnglish (US)
Pages (from-to)8561-8564
Number of pages4
JournalJournal of Biological Chemistry
Volume263
Issue number18
StatePublished - Jan 1 1988

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Weil, D., Bernard, M., Combates, N., Wirtz, M. K., Hollister, D. W., Steinmann, B., & Ramirez, F. (1988). Identification of a mutation that causes exon skipping during collagen pre-mRNA splicing in an Ehlers-Danlos syndrome variant. Journal of Biological Chemistry, 263(18), 8561-8564.