Fig. 3. Activation of the EGF receptor LET-23 promotes healthy aging.

(A) Activation of the EGFR let-23 extends swimming healthspan. The gain-of-function let-23 (sa62) mutant strongly increases swimming performance in advanced age. Data are for 25°C, though similar effects are observed also at 20°C. Error bars represent s.e.m. Unpaired two tailed t-test (N2 versus let-23 (sa62) mutant on each day), ***P< 0.0001.

(B) Disruption of EGFR activity accelerates swimming decline in aging animals. For swimming assay, the reduction-of-function let-23 (n1045) rf mutant and N2 wild type were grown continuously at restrictive temperature of 20°C. Error bars represent s.e.m. Unpaired two tailed t-test (N2 versus let-23 (n1045) mutant on each day), ***P< 0.0001.

(C) Age-related deterioration of C. elegans body wall muscle as indicated by GFP fluorescence decline of a p_myo-3NLS∷GFP fusion. The GFP reporter is localized to muscle nuclei, and becomes progressively sequestered and dims with age (Herndon et al., 2002). Representative whole-animal view of the wild type and the let-23 (sa62) gf mutant expressing GFP in the nuclei of body wall muscle at ages indicated (25°C). When the EGFR is activated, signal dimming occurs more slowly, consistent with muscle healthspan extension.

(D) Quantitation of the number of fluorescent nuclei in the wild type and the let-23 (sa62) gf mutant. 15 animals of each strain were scored in 2 independent trials. Error bars, s.e.m. P value for unpaired two-tailed t-test, ***P < 0.0001.

(E) Age pigments accumulate at a reduced rate when EGFR is activated. Representative same-exposure photographs of fluorescent species in the intestine of wild type N2 versus let-23 (sa62) mutants at day 11 (25°C).

(F) Measurement of AGE pigment accumulation for wild type N2 and let-23 (sa62) gf. AGE pigment scores were normalized as the relative fluorescence units for AGE pigments divided by tryptophan fluorescence. Data are from three independent experiments, 50 animals total for each strain; au arbitrary units, error bars, s.e.m.; P value, unpaired two-tailed t-test, *P < 0.01.

(G) The EGFR(gf) mutant exhibits enhanced lifespan, 20°C. Details of data in Table S3, Supporting information.

(H) The EGFR(rf) mutant is short-lived. For lifespan assay, strains were grown at permissive temperature of 25°C until day 5 after hatching, and then transferred to the non-permissive temperature of 15°C. Details of data in Table S3, Supporting information.