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Fig. 3 cGAMP is elevated in hearts from elderly zebrafish and regulates the expression of pml, Trex1, and plex9.1. (a and b) Gene expression analysis of zebrafish hearts from young and aged cohorts shows differences in innate immune signaling markers (a) and senescence markers (b). (c) γ-H2AX foci, a marker of senescence are present in a greater abundance of cells in the hearts of elderly zebrafish. Myocytes were visualized using a tg(myl7:eGFP) reporter that the transgenic animals express. Scale bar is 50 µm. (d) cGAS activity is elevated in the elderly zebrafish. 2′3′-cGAMP concentrations were determined from individual hearts isolated from young and aged zebrafish. (e) Gene expression analysis of the cGAS-STING pathway orthologs in axolotl indicate that plex9.1 expression is reduced in hearts from aged zebrafish. cgasb expression could not be detected in the zebrafish heart samples. (f) Treating cell lines derived from gar (GARL), axolotl (AL1), and zebrafish (ZKS) with cGAMP altered expression of the different cGAS suppressors. Gene expression in zebrafish hearts was compared with an unpaired, two-tailed Student's t-test (two-tailed). Variations between treatment groups was assessed with a one-way ANOVA, with Tukey's post hoc analysis for pairwise comparisons between treatments. *p < 0.05; **p < 0.01; ****p < 0.0001.