Gut-specific and Cre-mediated tert expression rescues gut aging phenotypes.a, Schematic representation of the transgene for Cre-inducible and tissue-specific expression of tert mRNA. b, RTβqPCR analysis of tert transgene mRNA and total tert mRNA (endogenous + transgene) expression in 9-month-old gut extracts (nWT = 5 and 6; ππ‘πππ‘β/βnoCre = 7 and 8 and ππ‘πππ‘β/β+Cre = 6 and 5 fish, respectively; levels were normalized by rps11 gene expression levels). c, Quantification of mean telomere length by TRF analysis (nWT = 7; ππ‘πππ‘β/βnoCre = 7 and ππ‘πππ‘β/β+Cre = 6 fish). d, Representative immunofluorescence images of DNA damage staining (Ξ³H2AX; left) and quantification (right; nWT = 6; ππ‘πππ‘β/βnoCre = 6 and ππ‘πππ‘β/β+Cre = 6 fish). e, Quantification of p53 protein levels (normalized by Ξ²-actin) analyzed by western blot (nWT = 6; ππ‘πππ‘β/βnoCre = 7 and ππ‘πππ‘β/β+Cre = 6 fish). f, Representative immunofluorescence images of proliferation staining (left, proliferation cell nuclear antigen (PCNA)) and quantification (right, nWT = 6; ππ‘πππ‘β/βnoCre = 6 and ππ‘πππ‘β/β+Cre = 6 fish). g, Representative image of SA-Ξ²-Gal staining. h,i, RTβqPCR analysis of the senescence-associated genes ink4a/b (p15/16) (h) and cdkn1a (p21) (i) expression (nWT = 6; ππ‘πππ‘β/βnoCre = 7 and ππ‘πππ‘β/β+Cre = 6 fish). j,k, Representative hematoxylin and eosin (H&E)-stained sections of the gut (j). The yellow arrows delineate the lamina propria width quantified in k (nWT = 7; ππ‘πππ‘β/βnoCre = 8 and ππ‘πππ‘β/β+Cre = 7 fish). l,m, RTβqPCR analysis of the YAP target genes cyr61 (l) and ctgf expression (m) (nWT = 6; ππ‘πππ‘β/βnoCre = 8 and ππ‘πππ‘β/β+Cre = 6 fish). n, RTβqPCR analysis of the junction protein-associated gene claudin-2 expression (nWT = 5; ππ‘πππ‘β/βnoCre = 7 and ππ‘πππ‘β/β+Cre = 6 fish). o, Representative immunofluorescence images of immune cell staining (left, L-plastin) and quantification (right, nWT = 6 fish; ππ‘πππ‘β/βnoCre = 6 fish and ππ‘πππ‘β/β+Cre = 7 fish). p, Representative immunofluorescence images of neutrophil staining (left, myeloperoxidase (MPX)) and quantification (right, nWT = 5 fish; ππ‘πππ‘β/βnoCre = 5 fish and ππ‘πππ‘β/β+Cre = 6 fish). All analyses are based on 9-month-old fish gut sections or extracts. Scale bar, 20 Β΅m. The dashed lines delineate the gut villi. All data are presented as the mean Β± s.e.m. *P < 0.05, **P < 0.01, ***P < 0.001, using a one-way ANOVA and post hoc Tukey test; *P < 0.05, **P < 0.01, using a KruskalβWallis and post hoc Dunn test.
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