Worm Breeder's Gazette 11(3): 72

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.

Suppressors of unc-52

Erin Gilchrist and Don Moerman

In unc-52 mutants movement is normal throughout the early larval 
stages, but the worms become progressively paralyzed as they age.  The 
onset of paralysis can begin as early as the L3 stage, or may not 
begin until after the final larval molt, depending upon the allele.  
At the cellular level, paralysis is correlated with the disruption of 
the normal oblique striations of the muscle fibers in the body wall 
muscle cells.  In completely paralyzed worms the birefringence in the 
muscle cells is very patchy and unstructured when viewed under 
polarized light.
In order to learn more about the role of unc-52 in maintaining 
normal muscle structure, we have been screening for reversion of the 
paralyzed phenotype.  Since the dense body is affected by mutations in 
unc-52, hopefully, some of the suppressors we have isolated will 
identify genes involved in the formation or maintenance of this 
structure.  A total of 44 revertants have now been isolated from 12 
EMS mutagenesis screens and one screen for spontaneous revertants (
~10+E7 animals per screen).  Two spontaneous revertants have also been 
found on stock plates.  Eighteen of the 35 strains analyzed have 
proven to be intragenic revertants which vary in phenotype from poorly 
moving (but better than unc-52) to almost wild type.  The remaining 17 
strains are extragenic suppressors of unc-52 and are similar in 
phenotype to the intragenic revertants.  None of the suppressor 
mutations appear to confer a phenotype on their own.  Six of the 
extragenic suppressors have been mapped, and all are on LGIV near dpy-
4.  This suggests that they may define a single gene.  One of these 
mutations suppresses all of the muscle-affecting unc-52 alleles, but 
the allele specificity of the other suppressors has not yet been 
determined.
At the cellular level, most of the body wall muscle cells in well-
moving, suppressed worms look wild-type, but some single cells show a 
slight patchiness which appears to result from the filaments detaching 
from the cell membrane.  Because movement is completely normal in some 
of these worms, the disruption of the normal striated pattern in the 
muscle cells may be due to stress during preparation for viewing under 
the microscope.  In wild-type worms this type of disruption is not 
seen, suggesting that suppression of unc-52 by these secondary 
mutations is not complete.