Worm Breeder's Gazette 11(1): 57

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.

More Gonadal Cell Migration Mutants

Ed Hedgecock, Ken Kowalkowski, David Hall and Joe Culotti

Figure 1

The complex trajectories of the hermaphrodite distal tip and male 
linker cells can be analyzed as successive segments of constant 
direction.  These directions are usually along a natural axis of the 
body wall although an oblique movement of the male linker cell (top 
right panel) may result from superimposed ventralward and 
posteriorward migrations.  Observations of selective loss-of-function 
tra-1 mutants and of tra-1 mosaics (C.  Hunter and W.  Wood, pers.  
comm.) suggest that the body wall carries only simple, static guidance 
cues common to both sexes and that complex gonadal cell trajectories 
are programmed cell autonomously, perhaps by changing cell receptors 
for these spatial cues.  mig-7(X) mutants may disturb the temporal 
program of gonadal cell migrations.  In mig-7 hermaphrodites, the 
distal tip cells fail to turn dorsalward near L3 lethargus but 
continue longitudinally along the ventral muscles.  In males, the 
linker cell fails to turn ventralward near L3 lethargus but stops 
migrating.  A possible, though hardly compelling, interpretation is 
that these cells repeat the navigational program of the previous 
larval stage, i.e., hermaphrodite distal tip cells continue 
longitudinally while male distal tip cells attempt to turn dorsalward. 
Interestingly, occasional seam cells in both existing mig-7 alleles 
divide near the L4 molt.  This phenotype is characteristic of lin-14 
gain-of-function mutants that repeat aspects of early larval stages (
Ambros and Horvitz, 1984).  We are currently testing whether the mig-7 
mutants are, in fact, novel lin- 14 alleles that repeat some L3 events 
during the L4 stage.  In mig-8(X) mutants (not shown), the 
hermaphrodites distal tip cell trajectory resembles the mig-7 
trajectory while the male linker cell trajectory is normal.  Distal 
tip cells in dpy-24(I) hermaphrodites usually turn dorsalward 
precociously and then continue centrifugally along the dorsal muscles. 
Often these cells reverse direction near the L3 molt suggesting that 
longitudinal movements may follow a normal temporal program while 
circumferential movements are misregulated.  Male linker cell 
trajectories appear normal.  As discovered by others, the linker cell 
migrations in him-4(X) males, and in a new mutant mig(rh155), are 
abnormal while the distal tip cells in hermaphrodites appear 
unaffected.  In summary, several genes affect the trajectories of 
either the hermaphrodite distal tip cells, the male linker cell, or 
both.  Some genes, e.g., unc-5 and unc-40, appear to affect 
directional cues while other genes may affect the temporal program.  
Double mutants could confirm some of these interpretations and suggest 
explanations for more exotic cell trajectories.
[See Figure 1]

Figure 1