Fig. 6

Fig. 6

BMP Signaling Is Required for Cardiomyocyte Dedifferentiation but Not Survival

(A) TUNEL staining on sections of myl7:GFP hearts at 7 dpi. Magnified view (boxed area) shows an example of an apoptotic cardiomyocyte (yellow arrow). Average absolute number of TUNEL+ cardiomyocytes per section found at the wound border at different time points post injury is plotted. Error bars represent SEM. Student’s t test, not significant (n.s.), p = 0.13 (1 versus 3 dpi), p = 0.45 (3 versus 7 dpi). Scale bars, 50 µm (overview), 12.5 µm (inset).

(B) The number of TUNEL+ cardiomyocytes at the wound border at 7 dpi does not significantly change in hsp70l:nog3 transgenics relative to heat-shocked wild-type siblings, while it is reduced in hsp70l:bmp2b transgenics. Error bars represent SEM. Student’s t test, p = 0.38 (nog3) (not significant), **p = 0.004 (bmp2b). Scale bars, 50 µm (overview), 12.5 µm (inset).

(C) Average percentage of pSmad1/5/8 expressing GFP^low and GFP^high cardiomyocytes in myl7:GFP transgenic hearts at 7 dpi. Error bars represent SEM. Student’s t test, *p = 0.014.

(D) Treatment of myl7:GFP transgenic fish with 5 µM dorsomorphin for 4 days significantly reduces nuclear pSmad1/5/8 accumulation in cardiomyocytes at the wound border at 7 dpi. Average percentage of cardiomyocytes expressing pSmad1/5/8 relative to DMSO control is plotted. Error bar represents SEM. Student’s t test, ***p = 0.0002.

(E) Cardiomyocyte dedifferentiation, as monitored by the size of the GFP^low area in myl7:GFP transgenic hearts at 7 dpi, is reduced upon BMP signaling inhibition either by treatment with 5 µM dorsomorphin or by noggin3 overexpression for 4 days. Error bars represent SEM. Student’s t test, *p = 0.013 (dorsomorphin), *p = 0.025 (nog3). Scale bar, 50 µm.