Fig. 2. Expanded expression of the EMT drivers Twist1, Snail, Slug and Sox9, and reduction of Cdh5 and Irx5 expression in the ventricles of Nkx2.5^Cre/+;Bmp2^tg/+ embryos.

a ISH showing Twist1, Snail, Slug, Cdh5 and Irx5 mRNA in E9.5 WT and Nkx2.5^Cre/+;Bmp2^tg/+ hearts. Black and yellow arrowheads mark expression or lack of expression in AVC mesenchyme cells, respectively; white arrowheads indicate expression in chamber endocardium. Cdh5 and Irx5 are transcribed in WT chamber endocardium, while are strongly reduced in the transgenic ventricle (black arrows). Scale bars 200 μm. b Confocal images of E9.5 WT and Nkx2.5^Cre/+;Bmp2^tg/+ hearts stained with Sox9 (green), IB4 (white), α-SMA (red) and DAPI (blue). Mesenchyme (1, arrowheads) and endocardial cells (1, arrow) in the WT AVC express Sox9, while IB4-positive endocardial cells of the right ventricle do not (2, yellow arrows). Nkx2.5^Cre/+;Bmp2^tg/+ hearts show Sox9-positive mesenchyme (3, arrowheads) and endocardial cells (3, arrows) in AVC, but also in the right ventricle (4, arrowheads and arrows). Scale bars 100 μm. Abbreviations as in Fig. 1