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Fig. 4 Loss of Mb promotes cardiomyocyte proliferation and regeneration in vivo (A) Western blot and quantification of Mb in WT and mb?/? zebrafish hearts; N = 3 biological replicates. (B) Representative western blot and quantification of pYAP and T-YAP WT and mb?/? zebrafish hearts; N = 3. (C) Zebrafish heart section demonstrating the staining for de-differentiation marker embCMHC in red and ?-sarcomeric actin in green at 7 days post amputation, and quantification of embCMHC cardiomyocytes (Differentiation index: % of cardiomyocytes expressing embCMHC in border zone of injury) from WT and mb?/? hearts; N = 3 from each group. Scale bar: 100 ?m. (D) Heart sections from WT and mb?/? zebrafish stained for Mef2c transcription factor (red) to identify cardiomyocytes and PCNA (green) to identify proliferating cells at 7 days post amputation: N = 7?9 individual zebrafish per group. Scale bar: 100 ?m. (E) Representative histological sections of AFOG stained tissue from WT and mb?/? zebrafish at 20- and 30-days post amputation stained to visualize fibrin (red), collagen (blue) and cardiac muscle (orange). Graph demonstrates the quantification of scar area on each section normalized to total ventricular area; N = 9?16 individual zebrafish per group. Scale bar: 100 ?m. Data are mean ± SEM. ?p < 0.05, ??p < 0.01, ????p < 0.0001.