Fig. 7

Fig. 7 Hh signaling is required for the initiation of fibronectin (fn1) expression in the ALPM region while fn1 function is required for endocardial differentiation. (A–F) Fn1 expression in the endocardial progenitors (arrows) is reduced in CyA-treated embryos (B,D,F) compared to DMSO-treated controls (A,C,E) at the 10-somite (A,B), 14-somite (C,D) and 18-somite (E,F) stages. (G–J) Fn1 expression is absent from the endocardial progenitors in smo MO (H) and shh + twhh MO mixture (J) -injected embryos as compared with uninjected controls (G,I) at the 16-somite stage. (K–P) Analysis of endocardial markers in nat/fn1-/- mutant embryos. (K,L) Endocardial kdrl expression is present at the midline in nat/fn1 homozygous mutant embryos (L), similar to their wild-type siblings at the 18-somite stage (K). (M,N) Endocardial NFATc1 expression is absent in fn1/nat mutants at 36 hpf. (O,P) Endocardial kdrl expression appears to be mislocalized and reduced in fn1/nat mutants at 32 hpf. Note that while the arrow points to the presumptive endocardial tube in nat mutants (P), it is not possible to reliably distinguish endocardial from vascular endothelial cells based on kdrl expression alone. All panels, ventral view of flat-mounted embryos, anterior is up. Individual nat mutant embryos were genotyped at the 18-somite stage following in situ hybridization as described previously (Garavito-Aguilar et al., 2010), while at older stages they were separated based on their morphological phenotypes.