Fig. 4. Gfra2 is downregulated in limbs and genitals in the absence of Hoxd gene function. (A) Ventral view of Gfra2 expression in right forelimbs. Gfra2 expression is first visible at E13.5 on the ventral side of the developing autopod. This domain is only weakly stained in HoxD^Del1-13 mutants. (B) Gfra2 is expressed strongly in the genital bud from the time of its emergence. By E13.5, the expression is much stronger in the distal half of the bud. In mutant genitalia, the expression is reduced and is more distally restricted at all days stained. (C) Real-time RT-PCR analysis quantifies and confirms the differences observed by WISH.