Figure 2. Nrg1 signaling modulates cardiomyocyte proliferation during regeneration.
(A and B) Section images of injured ventricular apices of animals treated from 6 to 7 dpa with DMSO (A) or 10 µM AG1478 (B) and stained for Mef2+PCNA+ cells (arrowheads). Wounds are indicated by dotted lines. Scale bar represents 100 µm. (C and D) Section images of 7 dpa ventricular apices of control β-act2:BSNrg1 (C) or cmlc2:CreER; β-act2:BSNrg1 (D) animals treated with tamoxifen at 3 days before injury, stained for Mef2+PCNA+ cells (arrowheads). Scale bar represents 100 µm. (E) Quantification of cardiomyocyte proliferation at 7 dpa. DMSO-treated wild-type clutchmates (n = 22) were used as controls for 10 µM AG1478 treatment (n = 20), and tamoxifen-treated β-act2:BSNrg1 clutchmates (n = 15) were controls for cmlc2:CreER; β-act2:BSNrg1 (n = 18) animals. Data are represented as mean ± SEM. *p < 0.05, Mann–Whitney Ranked Sum Test. (F) Cartoon schematic of β-act2:BSNrg1 transgene. (G) RT-PCR results for erbb2, erbb4a, and erbb4b, indicating the presence of erbb2 and erbb4b messages in the uninjured adult ventricle. cmlc2 is shown as a control. (H) Section image of RNAscope in situ hybridization analysis for nrg1 expression at 14 days after tamoxifen-released expression in uninjured cmlc2:CreER; β-act2:BSNrg1 ventricles. (I) Section image of RNAscope in situ hybridization analysis for EGFP expression in uninjured cmlc2:actinin3-EGFP ventricles, used as a control to detect transgenic signals. Scale bar represents 100 µm.