Fig. 2

Fig. 2 Bmp regulates LR patterning at two distinct developmental time points. (A–E) Spw expression in the LPM and ntl expression in the midline in wild-type (A), Tg(hs::noggin3) (B, C) and Tg(hs::bmp2b) (D, E). Heat-shock induced noggin3 expression at tb stage results in bilateral spw expression (B) while noggin3 induction at the 16-somite stage has no effect on spw expression (C). Heat-shock induced bmp2b expression at the tb stage results in the absence of spw expression (D) while bmp2b induction at the 16-somite stage has no effect (E). (F–J) At the 22 somite stage pitx2 is asymmetrically expressed in the LPM (F, arrow). Left-sided pitx2 expression is absent in Tg(hs::noggin3) embryos heat-shocked at the tb stage (G). Normal left-sided pitx2 expression in Tg(hs::noggin3) embryos heat-shocked at the 16 somite stage (H). Bilateral pitx2 expression in the LPM of Tg(hs::bmp2b) embryos heat-shocked at the tb stage (I). Normal left-sided pitx2 expression in Tg(hs::bmp2b) embryos heat-shocked at the 16 somite stage (J). (K–O) Lefty1 expression in the midline and left cardiac field at the 22-somite stage of a wild-type embryo (K). Induction of noggin3 (L, M) or bmp2b (N, O) at tb or 16-somite stage, results in the down-regulation of lefty1 in the cardiac field. In the notochord, lefty1 expression is repressed by ectopic noggin3 (L, M) and induced by bmp2b (N, O). (P–T′) Lefty2 expression in the left cardiac field of a 25-somite stage wild-type embryo (P). Induction of noggin3 at the tb (Q) or 16-somite stage (R) or the induction of bmp2b at the tb stage (S) results in the down-regulation of lefty2 expression. Induction of bmp2b expression at the 16-somite stage results in ectopic lefty2 expression in the right cardiac field (T, arrowhead) and in the notochord (T2). (U–W) Foxa3 expression in the visceral organs of a wild-type embryo at 50 hpf (U). Induction of noggin3 at the tb stage results in visceral organ laterality defects, such as organ duplications and absence of gut looping (V) while ectopic noggin3 expression induced at the 16-somite stage has no effect on the laterality of the visceral organs (W). All embryos are shown as dorsal views with anterior to the top of the panel.