Worm Breeder's Gazette 16(2): 33
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.
Department of Zoology, University of British Columbia, Vancouver, B.C. Canada
Embryos homozygous for mutations in the unc-52, pat-3 and unc-112 genes of C. elegans exhibit a similar Pat phenotype. Myosin and actin are not organized into sarcomeres in the body wall muscle cells of these mutants, and dense body and M-line components fail to assemble (Williams and Waterston, 1994, JCB 124:475). The unc-52 (perlecan) and pat-3 (b-integrin) genes encode ECM or transmembrane proteins found at the cell-matrix adhesion sites of both dense bodies and M-lines. We have determined that the unc-112 gene encodes a novel, membrane-associated, intracellular protein that co-localizes with integrin at cell-matrix adhesion complexes. The 720 amino acid UNC-112 protein is most similar to a human protein of unknown function called Mig-2 (Wick et al. 1994, J. Cell Sci.107:227), and shares a region of homology with talin and other members of the FERM superfamily of proteins. A functional UNC-112::GFP protein is expressed in the body-wall muscle of embryos, and in the body-wall, vulval, spermathecal, uterine, and anal sphincter/depressor muscle cells of adult hermaphrodites. In body wall muscle, UNC-112::GFP co-localizes with PAT-3/b-integrin at dense bodies, M-lines and adhesion plaques. We have identified the sequence alterations corresponding to the four known unc-112 alleles. The EMS-induced st562 and st581 mutations are single nucleotide alterations that introduce stop codons into the unc-112 coding sequence. The formaldehyde-induced gk1 allele obtained from the C. elegans Reverse Genetics Core Facility is a 2.18 kb deletion. Embryos homozygous for these three null mutations exhibit a Pat terminal phenotype. They arrest at the two-fold stage of embryogenesis and have severely disorganized body wall muscle. In contrast, animals carrying the r367 allele of unc-112 are viable, although they do have disorganized body wall muscle and are paralyzed as adults. The r367 lesion is a missense mutation in the amino-terminal region of the protein that results in a Thr to Ile change. Our analysis of unc-112(st581) mutant embryos using the MH2, MH24 and MH25 mAbs (Francis and Waterston, 1985, JCB 101:1532) has revealed that UNC-112 is required to spatially organize PAT-3/b-integrin clusters after they are integrated into the basal cell membrane, but is not required to organize UNC-52/perlecan in the basement membrane nor for DEB-1/vinculin to associate with PAT-3/b-integrin. We also have determined that UNC-112 requires the presence of UNC-52/perlecan and PAT-3/b-integrin, but not DEB-1/vinculin for its proper localization in the muscle cell membrane. In summary, we have identified a new component of cell-matrix adhesion structures, the ~80 kD UNC-112 protein. We have shown that UNC-112 co-localizes with PAT-3/b-integrin, and that each of these proteins is required for the correct distribution of the other in the muscle cell membrane. We expect that the human ortholog of UNC-112, the Mig-2 protein, will also be associated with adhesion complexes.