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Figure 2 (A–F) Direct comparison of frnt with young adult, (A, D) and naturally aging wild-type zebrafish (2.5 years; (B, E). Similar degenerative pathologies are shared between aged zebrafish (B, E) and 8 month-old mutants (C, F), such as fibrosis and sarcopenia of slow muscle fibers (B, C), and thinning skin (E, F). (G–I) Characterization of slow muscle phenotype in frnt mutants. (G) Expression analysis of stem cell marker paired-box 7a (pax7a, n = 6) and (H) cdnk1a/p21 control in slow muscle from 7 month old homozygous (n = 6) and heterozygous mutant fish (n = 9). (I) Adult frnt has smaller fiber size in slow muscle compared to age-matched wild type and sibling fish (3 month (n = 5) and 9 month old (n = 9), but not as juvenile fish (3 week old, n = 3). (J–L) Changes in epidermal phenotype in frnt mutants. (J) Expression of the stem cell marker delta-Np63 and (K) control claudin-b in epidermal tissues from 7 month old homozygous (n = 12) and heterozygous (n = 5–6) frnt fish. (L) Count of DAPI positive basal cells in the integumentary epithelium in 3 (n = 3–4) and 9 month old (n = 5) frnt fish. (M–N). DAPI stained epidermal nuclei in wild-type (M) and frnt (N) mutant epidermis. Error represented as mean +/- standard deviation. ****p<0.0001, *p<0.05.