Fig. 6. Gene expression analysis in hindlimbs of Isl1Cre/+;Bmpr1a mutants and wild-type littermate controls. Aberrant dorsal ventral patterning in mutants is evidenced by decreased expression of En1 in ventral ectoderm (A-D,F-I), and ventral expression of Lmx1b (E,J). En1 continues to be expressed in AER of mutants, but AER expression is sometimes disrupted or split (arrows H,I). Fgf8 expression in AER is broadened and ectopically expressed in mutant hindlimbs (K,L,Q,R). Fgf10 expression appears normal (M,N,S,T), whereas Bmp4 expression is decreased in mutants (O,P,U,V). Anterior-posterior patterning and the zone of polarizing activity appear normal in both endogenous and ectopic hindlimb structures, as evidenced by expression of Hand2 (dHand), Gli3, gremlin and Shh (W-L'). In Isl1Cre/+;Bmpr1a mutants, expression of Tbx4 and Tbx5 is unaffected (M',N',S',T'); Tbx2 expression is somewhat reduced in limb and interlimb regions (arrows O',P',U',V'); and Tbx3 expression is severely reduced throughout the limb (arrows Q',R',W',X'). A, anterior; P, posterior; Lat, lateral view; Ven, ventral view; Dor, dorsal view. Arrows in E, Z and H' indicate tissue between the two hind limbs.