Fig. 3.

Hypomorphic mutations in MC4R cosegregate with hyperphagia. (A) Protein sequences of A. mexicanus MC4R [adapted after Tao (18)] shown in red are Tinaja-specific mutations. (B) Dose–response curve of Tinaja and surface alleles in vitro using 293T cells. Tinaja cavefish have a lower maximal response and basal activity than surface fish (P < 0.05). Each data point represents the mean of three wells being independently transfected and measured. (C) Appetite comparison between Pachón cavefish crosses carrying either the surface or cave allele of MC4R. C, Tinaja cave allele; S, surface allele. Twenty-two homozygous fish and 38 heterozygous fish (3-mo-old) were used, and their appetite was assayed over a 1-wk assay period. **P < 0.005 (two-tailed t test). (D) Body length comparison among Pachón cavefish MC4R genotypes. The same fish shown as in Fig. 3C, but 6 mo older. At the end of the experiment, the fish were 9 mo old. (E) Percentage of weight loss comparison among Pachón cavefish MC4R genotypes during a 3-wk fast. Same fish as in Fig. 3D were used, but they were starved after measuring length. *P < 0.05 (two-tailed t test).