Worm Breeder's Gazette 14(3): 60 (June 1, 1996)
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.
Pathology Dept, Robert Wood Johnson Medical School, Piscataway NJ 08854.
Laminin, a major constituent of the extracellular matrix, is
composed of 3 subunits, a, B and y (formerly A, B1 and B2) which are
linked by covalent and non-covalent bonds. In worms epi-1 codes for the a
chain and lam-1 for the B chain. The third subunit has now been found by
the worm sequencing project on the X chromosome on C54D1. Sequence
comparison shows that it possesses all the hallmarks of a bona fide member
of the family. It is very similar to the fly y gene, being 59% identical
in domain VI, 62% in domain V, 42% in IV, 53% in domain III and 13% in the
predicted coiled -coil domains II & I.
Having all the subunits in hand, we can now systematically study the
contributions of each of the subunits to the basement membrane assembly
and function. The unc-6 gene product is largely "y-like" in its
laminin-related domains. We can now ask whether these "y-like" regions of
UNC-6 are an evolutionary accident of the duplication of the nearby
laminin y gene, or whether they confer some character to the protein that
cannot be given by the related domains in the a and B subunits.
Northern analysis reveals a transcript of approx 4 kb, as expected
by its coding capacity, as well as a smaller transcript of 1.5 kb. This
smaller transcript may be an alternatively spliced form, and we plan to
perform RT-PCR experiments to investigate this. We have so far identified
partial cDNAs for the gene. Analysis of embryonic expression by in situ
hybridization using the method of Seydoux & Fire shows that the gene is
expressed broadly during embryogenesis. However neither Seydoux nor Fire
would be impressed by the quality of the embryos in the experiments and we
are repeating them try to find more precisely which cell types express
this gene. It is of interest to find which tissues express this ECM
component, since work by the Kramer lab has raised the possibility that
not all tissues that possess the type IV collagen in their ECM, synthesize
it. We have also constructed 2 GFP fusions to the genomic clone to address
this issue. We are also initiating a search for mutations in this gene
based on the expectation that the mutant phenotypes for this gene will
resemble those for epi-1 and lam-1.