Figure 4. The ced-4 core apoptotic gene, but not known C. elegans upstream regulators of developmental, germline, or radiation-induced apoptosis, are needed for efficient axonal regeneration.

(a) We measured mean regenerative outgrowth in ALM neurons 24 h after laser surgery for WT and mutant strains affecting ced-3 and ced-4 (two independent alleles) core apoptotic genes, compound mutants, and in ced-4; Is[p_mec-4ced-3]. Because some studies [9],[10],[18] documented mutant neurons that show virtually no post-axotomy regeneration and we find that the kgb-1 ced-3 double mutant exhibits lower regeneration than the ced-3 single mutant (Figure S6), the partial phenotype can become more severe in compound mutants. (b) Regenerative outgrowth was measured 3 d after surgery in ALM neurons in WT and ced-4(n1162) (no statistical difference by t test). (c) Regenerative outgrowth was measured 24 h after surgery in ALM neurons for mutants in upstream apoptosis regulators as well as compound mutants (which show no statistical difference by one-way ANOVA test). Bar graphs depict mean ± s.e.m. For (a), the Student's t test, with a Dunn-Sidak adjustment for multiple comparisons, was used to determine the statistical significance of differences versus WT, with brackets indicating direct Student's t test between two specific values. *p<0.05, **p<0.005.