Fig. 9

Hoxb1b regulates FGF signaling.

Fgf3 is expressed in r4 in wildtype embryos (A) and hoxb1a^−/− mutants (B). Fgf3 expression is lost in hoxb1b^−/− mutants (16/16 embryos) (C) and hoxb1a^−/−;hoxb1b^−/− mutants (4/4 embryos) (D). Fgf8 is expressed in r4, medial r2 and the MHB (E). The loss of hoxb1a reduces the space between r2 and r4 and the MHB becomes arrowhead shaped (14/19 embryos) (F). In hoxb1b^−/− mutants (19/19 embryos) (G) and hoxb1a^−/−hoxb1b^−/− mutants (8/8 embryos) (H) there is ectopic expression of fgf8 in r3 and reduced expression in the lateral portions of r4. The expression of FGF responsive genes, pea3 (I–L), dusp6 (M–P), spry1 (Q–T), spry2 (U–X), and spry4 (Y–B′) are unaltered from wildtype (I,M,Q,U,Y) in hoxb1a^−/− mutants (J,N,R,V,Z). In both hoxb1b^−/− mutants (pea3: 6/7 embryos, dusp6: 10/11 embryos, spry1: 25/25 embryos, spry2: 19/19 embryos, spry4: 23/23 embryos) (K,O,S,W,A') and hoxb1a^−/−;hoxb1b^−/− mutants (pea3: 6/6 embryos, dusp6: 5/5 embryos, spry1: 9/9 embryos, spry2: 5/5 embryos, spry4: 4/4 embryos) (L,P,T,X,B′) there is an increase in expression levels. Spry1 and spry2 show ectopic expression in r3 (S,T,W,X), while spry4 is ectopically expressed in r4 (A′, B′). All embryos have been genotyped for hoxb1a^sa1191 and hoxb1b^ua1006. All images are dorsal views, anterior to the left, 4 somites.