Fig. 1

Heart Cryoinjury Augments Telomerase Activity and tert Expression Levels

(A) Representative telomeric repeat amplification protocol (TRAP) activity in uninjured (UI) hearts and hearts at 1, 3, 4, 7, and 30 days post cryoinjury (dpi) (n = 3/condition and time point). Positive control (C+), iPSCs; negative control (C), tert^-/- zebrafish heart; reaction specificity control, uninjured + RNase. LB, lysis buffer.

(B and C) Telomerase TRAP activity assay in 6- and 10-month-old zebrafish hearts (n = 4/time point). Data are means ± SEM. ns, not significant (unpaired Student’s t test).

(D) Zebrafish tert mRNA expression levels in homeostasis and during regeneration (3 dpi) (n = 4 hearts/condition). CPMs, counts per million. Values are means ± SEM. p < 0.001 (B–H adjusted p value).

(E) Representative TRAP assay showing the lack of telomerase activity in tert^-/- hearts (n = 3/genotype).

(F) Lack of telomerase does not affect heart development and function. There is normal anatomy and function in tert^-/- zebrafish hearts. Shown are whole-mount views of dissected adult WT and tert^-/- uninjured zebrafish hearts (left) and Masson-Goldner trichrome-stained sagittal sections (center). Five animals were analyzed per genotype. V, ventricle; At, atrium; BA, bulbus arteriosus. Scale bars, 100 µm.

(G and H) Echocardiographic evaluation of heart size (ventricular volume (VV) in diastole) (G) and cardiac function (ventricular FVS) (H) in uninjured WT and tert^-/- animals. Values for both parameters did not differ between genotypes. Circles and squares show data for individual animals. Horizontal bars represent the mean (unpaired Student’s t test). A total of 17–20 animals were analyzed per genotype.