Worm Breeder's Gazette 10(2): 74
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Basement membranes(BMs) are believed to be involved in tissue morphogenesis, maintenance of tissue architecture, as well as cell movement and attachment. Although BM components have been studied intensively at the biochemical level, there has been no means to study the functions of these components genetically. We are interested in identifying the genes that encode BM components and in performing molecular and genetic studies of the functions of BM in development. Using fragments of a mouse Type IV (BM) collagen cDNA as probes, we have identified two clones containing BM-like collagen genes (CH#1 and CH#2) from a C. elegans genomic sublibrary of collagen containing phage. The two genomic clones were isolated by screening the sublibrary with a fragment of the mouse Type IV collagen cDNA that does not contain any Gly-X-Y coding sequence and does not cross hybridize to other collagen genes. Under relatively high stringency conditions, CH#1 and CH#2 hybridize more strongly to the Gly-X-Y portion of the mouse Type IV cDNA than do any of the other C. elegans collagen clones. CH#1 and CH#2 have been restriction mapped and both genes span about a 6-7 kb region within the clones. The restriction maps are different from each other indicating that these two genes encode two distinct alpha polypeptide chains of Type IV collagen. Both clones were radioactive labeled and probed to Northern blots. The results show that both genes produce 5.5 kb long transcripts, similar in size to the mouse and human Type IV collagen transcripts, but much larger in size than the C. elegans cuticle collagen transcripts. CH#1 and CH#2 have been placed onto contigs by the MRC group. The genetic location of the CH#1 contig is not known. CH#2 has been mapped to linkage group III, about 100 kb to the right of the lin-12 locus. Several embryonic lethal genes are located in this region. We have examined mutants of these genes briefly. One of these genes, emb- 9, has temperature sensitive mutant phenotypes that could result from defects in BM. Morphologically, emb-9 appears very similar to let-2, a gene previously found to cause BM defects (J. Kramer and J. Priess). Two of the five emb-9 alleles are semidominant, suggestive of a structural protein like a BM collagen. emb-9 is being analyzed to determine if it is the CH#2 BM collagen gene, and this may provide the means to begin a genetic analysis of BM structure and function.