Worm Breeder's Gazette 9(1): 51

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.

A Pseudo Wild Type Mutation, sc109, That Suppresses Blister Formation

M. Kusch and R.S. Edgar

We isolated and partially characterized a recessive cuticle mutation,
sc109, that suppresses formation of blisters.  While animals 
homozygous for sc109 have marked cuticle protein differences when 
compared to N2, mutants cannot be readily distinguished from wild-type 
when viewed with a dissecting microscope.  The most straight-forward 
interpretation of our results is that the sc109 locus affects post-
translational processing of cuticle proteins (as is probably also the 
case for at least some bli mutations).  Other explanations cannot yet 
be ruled out however.
The sc109 mutation was obtained in a strain carrying a bli-1 allele 
by selecting F2 wild-type revertants following EMS mutagenesis of bli-(
sc73)II hermaphrodites.  The sc109 locus is on LGV, but has not been 
mapped further.  While sc109 hermaphrodites appear wild-type, males 
sometimes have small tail blisters which are a slight impediment to 
sinusoidal movement, but do not prevent mating.
In addition to suppressing blister formation in bli-1(sc73) animals, 
sc109 suppresses blisters in bli-2(e768), 7) and 
bli-6(sc16) mutants.  Alleles of bli-3 and bli-5 were not examined.  
Suppression is not always complete in hermaphrodites, as small blips 
can be found on occasional animals.  In males, suppression is almost 
never complete and above their bursa small blisters appear that 
enlarge somewhat with age.  However, newly molted males are fertile 
and mate well.  Suppression may be specific for bli mutations since 
several dpy and col mutations were not affected by sc109; however, 
this question was not addressed systematically.
Cuticles of sc109bli-1(sc73) double mutants differ from those of 
both the bli-1 parent and N2 when examined by transmission electron 
microscopy (TEM) and scanning electron microscopy (SEM).  In TEM s of 
bli-1 cuticles, a large space, presumably corresponding to the blister 
in live animals and containing much electron dense material is 
apparent between the cortical and basal layers.  This space is gone in 
the sc109 containing revertant.  In addition, the cuticle of the 
revertant is one-third to one-half as thick as that of N2 animals.  We 
have not seen struts in revertant cuticles either by TEM or by phase 
contrast microscopy, examination by SEM revealed ill-formed alae 
appearing as three rows of small bumps running head to tail with 
various-sized spaces between the bumps of a single row.
Cuticle proteins isolated from sc109 animals were separated by SDS-
PAGE and stained.  Animals carrying sc109, in the presence or absence 
of bli-1(sc73), had 25-33% as much soluble cuticle protein per animal 
as N2.  While electrophoretic profiles of wild-type and bli-1 cuticle 
proteins were identical, sc109 cuticles had much less of a major 
protein band, cpD (MW~100,000) and no apparent cpF (MW~200,000) a 
minor band.  Less pronounced quantitative differences were apparent 
for other cuticle proteins.  When sc109 cuticle proteins were 
separated by 2D gel electrophoresis (IEF followed by SDS-PAGE) and 
visualized by Western blotting, we found identical spots with mutant 
and wild-type cuticle proteins, but quantitative differences were