Fig. S1

Fig. S1 Bmp signaling regulates hand2 expression in the lateral plate mesoderm (LPM)
(A-B) Transverse section of Tg(hand2:EGFP) embryo stained with hand2 in situ probe (red), anti-GFP antibody (green), and Topro to label the nuclei (blue). Both hand2 mRNA and Tg(hand2:EGFP) are expressed in the ventral half of the LPM, and the most medial LPM cells appear to downregulate hand2 expression.
(C-E) Expression of hand2 in wild-type (C), Tg(hsp70l:bmp2b)^f13 (D), and Tg(hsp70l:dnBmpr- GFP)^w30 (E) embryos that were heat-shocked at the 5-somite stage (11.66 hpf) and fixed at the 15-somite stage (16.5 hpf). Bmp2b overexpression leads to an expansion of hand2 expression, while blocking Bmp signaling slightly reduces it by the 15-somite stage. (F-G) Tg(hand2:EGFP) expression in wild-type (F) and Tg(hsp70l:bmp2b)^f13 (G) embryos that were heat-shocked at the 5-somite stage and fixed at 30 hpf. Heat-shocked Tg(hsp70l:bmp2b)^f13 embryos expressed Tg(hand2:EGFP) throughout the LPM, and the epithelial polarity of the LPM cells seemed to be affected. White dashed lines outline the LPM and yellow dashed lines mark the midline.
(H-I) Inhibiting Bmp signaling by heat-shocking Tg(hsp70l:dnBmpr-GFP)^w30 embryos at the 5- somite stage abolished hand2 expression in the LPM (asterisk) by 30 hpf. (J-K) Tg(hsp70l:dnBmpr-GFP)^w30 embryos expressed the LPM marker wnt2bb after heat-shock at the 5-somite stage. Dashed lines mark the notochord and LPM. (L-M) As revealed by phalloidin labeling, Tg(hsp70l:dnBmpr-GFP)^w30 embryos failed to undergo leftward gut looping after heatshock at the 5-somite stage. White dashed lines outline the LPM and yellow dashed lines mark the midline.
(C-E, H-I) Dorsal views, anterior to the top. (A-B, F-G, J-M) Transverse sections, dorsal to the top. L, left; NC, notochord; R, right. Scale bars, 40 μm.