Worm Breeder's Gazette 11(4): 64

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.

The V-2 EGF-like Domain of the unc-6 Laminin Chain is Required for Dorsal Cell and Axon Migrations

William Wadsworth and Naoaki Ishii

Figure 1

The unc-6 gene encodes an unusual laminin B2 chain (~2.7 kb mRNA).  
The first 7 exons of the gene have been sequenced and the predicted 
protein is homologous to the N-terminal domains V and V1 of known 
laminin B chains (1).  Domain V1 is globular and domain V consists of 
EGF-like repeats.  Mutations in the unc-6 gene affect dorsal and 
ventral cell migration guidance (2).  The unc-5 gene has been shown to 
act in combination with unc-6 to affect dorsal cell migrations.  The 
predicted protein product of the unc-5 gene is a transmembrane 
receptor (3).  Four unc-6 alleles, rh69, rh202, rh204, and rh402, 
selectively disrupt dorsal cell migrations.  We have examined these 
mutations in detail since they might define a domain of the laminin 
molecule involved with binding to the unc-5 receptor.
Restriction fragment polymorphisms were found in the DNA of strains 
with the rh202, rh204, or rh402 allele.  The polymorphisms were mapped 
and PCR was used to clone the DNA sequence.  As shown below, the three 
alleles have deletions of the region containing the coding sequences 
for the second EGF-like repeat in domain V.  The fourth allele, rh69, 
was found to be a point mutation in a splice consensus sequence of the 
small intron within the V-2 coding sequence.  We have not yet looked 
at the RNA splicing patterns in these strains, however we speculate 
that the exons for repeats V-1 and V-3 are spliced together, creating 
a slightly smaller protein lacking repeat V-2.
[See Figure 1]

Figure 1