Fig. 3. lin-39 and ceh-20 are likely to act through egl-1 in the VC neurons. For all genotypes, the expression pattern of the P_lin-11gfp reporter was scored in 50 animals. (A,B) The P_lin-11gfp reporter is expressed in the six VC neurons of wild-type animals [average of 4.4 cells; two VC neurons (VC4 and VC5) are often obscured by vulval and sex muscle expression, and are not scored] and in the VC-like neurons that survive in an egl-1 mutant (average of 8.7 cells from P2-P12 descendants) (Cameron et al., 2002). (C,E) VC neurons undergo programmed cell death in lin-39 mutants (average of 0 cells). VC and VC-like neurons survive and express P_lin-11gfp in lin-39; egl-1; P_lin-11gfp mutants (average of 9.0 cells). In lin-39 mutants, the P cell descendants migrate abnormally far forwards (Clark et al., 1993). (D,F) Many VC neurons die in ceh-20(ay9) mutants. In ceh-20(ay9); egl-1; P_lin-11gfp mutants, the VC and VC-like neurons survive and express P_lin-11gfp but the fluorescence is of variable brightness, especially in the anterior nerve cord (average of 7.4 cells). (G) In ceh-20(ay42); egl-1; P_lin-11gfp mutants, the VC and VC-like neurons survive but do not express P_lin-11gfp (average of 0 cells). Direct observation of cell lineages in the ceh-20(ay42); egl-1; P_lin-11gfp mutant confirmed that the VC neurons did not undergo programmed cell death. Arrowheads indicate nuclei of VC and VC-like neurons.