MOLECULAR BIOLOGY OF COLLAGEN TYPES V AND VII

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DESCRIPTION: This proposal comprises studies of type V collagen and its roles in human diseases and studies into the tissue-specific expression of the type VII collagen gene. Studies will include: 1) The role of type V collagen in Ehlers-Danlos syndrome (EDS). Molecular defects have yet to be reported in the type V collagen of humans. However, a patient with EDS and hypomelanosis of Ito has a balanced (X;9) translocation and appears to have a chromosomal breakpoint within the alpha 1(V) collagen gene (COL5A1). The nature of the rearrangement within COL5A1 will be determined to provide insights into translocation mechanisms and into the molecular basis of the phenotype in this EDS patient. In a more far-reaching study, molecular probes will be developed for PCR-based scanning for mutations in type V collagen DNA and RNA sequences of EDS patients. Probes developed in these studies will be used to survey a unique clinical resource comprising RNA and genomic DNA from 590 EDS patients in whom collagen types I and III are normal. Probes and strategies developed in these studies will be of use to other researchers studying heritable connective tissue disorders. 2) Characterization of the pro-a3(V) collagen chain. Pro-a3(V) is the only type V collagen chain for which a complete primary structure and nucleic acid probes are not available. Full-length cDNA sequences will be isolated, providing the pro-a3(V) structure and providing probes for detailed characterization of the tissue distribution of pro-a3(V) RNA. Rigorous examination of the co-expression of the various collagen type V/XI chains by in situ hybridization of fetal and adult mouse tissues should provide insights into roles of the various combinations of V/XI chains in development and homeostasis. The a3(V) gene will be mapped in mice and humans to determine whether it colocalizes with loci for heritable abnormalities. Probes will be developed to assay for pro-a3(V) defects in the panel of EDS patients described above. 3) Transcription controls of type VII collagen gene, COL7A1. Mechanisms governing the highly tissue-specific expression of COL7A1 will be explored. Studies will include functional assays in cell culture and transgenic mice and further characterization of cis-acting elements by mutation analyses and for ability to bind specific nuclear factors. New insights should be provided into how differentiation- and tissue-specific expression is achieved in certain ethelia. COL7A1 cis-acting elements also have potential to help achieve edermis-specific expression of medically useful genes in gene therapy.