Fig. 8. Blocking of FGF receptor activity results in loss of lmx1b.1 and lmx1b.2 expression at the developing IsO. (A,B) Four hours of exposure to SU5402 beginning at the tailbud stage eliminates expression of both lmx1b.1 (A) and lmx1b.2 (B) at the developing IsO, while expression at the midline is unaffected. (C,D) Exposure to DMSO alone does not affect expression. Red arrowheads indicate the position of the MMR and white arrowheads indicate missing MMR staining.