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. 2012 Mar 8;7(3):e32991. doi: 10.1371/journal.pone.0032991

Figure 3. Mab21l2 is required for the formation of the proepicardium and the epicardium.

Figure 3

(A,B, E–H, M–T) In situ hybridizations of sagital (A, B, E–H) and transverse (M–T) paraffin sections of E9.5 and E11.5 WT and Mab21l2 mutant embryos for the transcripts indicated. (C, D, I–L) H&E-stained transverse sections of E9.5 and E11.5 WT and Mab21l2 mutant embryos. Mab21l2 expression was detected in the proepicardium (arrowhead) of E9.5 WT embryos (A and B). Compared to WT embryos (C), the proepicardium (arrowhead) was absent in Mab21l2 mutant embryos (D). Expression of the proepicardial and epicardial marker genes, Tbx18, and Wt1, was compared between WT ([E] Tbx18; [G] Wt1), and Mab21l2 mutant embryos ([F] Tbx18; [H] Wt1), showing that the proepicardium is significantly small in Mab21l2 mutant embryos. In E11.5 WT embryos (I and J), the epicardium (arrowhead) occurs between the compact myocardium and the body wall (arrows), but in Mab21l2 mutant embryos (K and L), the epicardium is absent. The expression of epicardial marker genes was detected in E11.5 WT epicardium ([M and N] Tbx18; [Q and R] Wt1), arrowheads), but not in Mab21l2 mutant embryos ([O and P] Tbx18; [S and T] Wt1), between the compact myocardium and the body wall (arrows). a, atrium; v, ventricle; la, left atrium; lv, left ventricle; ra, right atrium; rv, right ventricle; sv, sinus venosus. Scale bars represent 30 µm (C and D), 50 µm (A, E–H), and 100 µm (I, K, M, O, Q and S).