Worm Breeder's Gazette 9(2): 63

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Update on Mutants Defective in Embryonic Cell Migrations

J. Manser and W.B. Wood

Figure 1

We have continued our study of mutations affecting the long range 
embryonic migrations of the neurons CAN, HSN and ALM (see 1985 C.  
elegans Meeting Abstracts, p.  18).  To date we have studied six 
mutations that define five loci and can be divided into two phenotypic 
classes (see table below).  In Class-1 mutants [mig(ct41) III and mig-
2(rh17) X], the CAN, HSN, and ALM migrations are all partially 
defective with high penetrance.    In Class-2 mutants [vab-8(e1017 and 
ct33) V, mig(ct73) V, and mig(7a) III], CAN migration is defective 
with high penetrance whereas defects in HSN and ALM migrations with 
much lower penetrance vary among the mutants as shown in the table.  
mig(ct73) V and mig(7a) III are recently acquired mutants.  mig(ct73) 
V was isolated by us as a spontaneous mutant that appeared on an N2 
stock plate.  mig(7a) III was isolated by Eve Wolinsky (MIT).  Both 
mutants were recognized by their skinny tails, a phenotype attributed 
to CAN misplacement in vab-8 animals (Sulston and Hodgkin, WBG vol.  5.
, No.  1, p.19).  mig(ct73) V complements vab-8(e1017) V, and mig(7a) 
III complements mig(ct41) III.  CAN migration is less severely 
affected in mig(ct73) V and mig(7a) III than it is in vab-8 V.  In 
most vab-8 animals, CAN migration is apparently completely abolished: 
the CAN nucleus is found over the nerve ring in the head (Sulston and 
Hodgkin, loc.  cit.; B.  Stern, 1985 C.  elegans Meeting Abstracts).  
In most mig(ct73) V and mig(7a) III L1's, CAN is seen partway between 
its position of birth and its normal postembryonic position (Nomarski 
optics).  Three double mutants have been constructed, characterized, 
and found to show additive effects of the two mutations.  Double 
mutants carrying either of the Class-1 mutations mig(ct41) III or mig-
2(rh17) X and a vab-8 mutation appear to exhibit completely defective 
CAN migration, while HSN and ALM migrations are partially defective 
with high penetrance.  A double mutant carrying both of the Class-1 
mutations, like mutants, exhibits partially defective CAN, HSN, and 
ALM migrations, but these nuclei tend to remain closer to their 
positions of birth in the double mutant.
[See Figure 1]

Figure 1