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.
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]