Fig. 1. Ift88^hypo limbs exhibit polydactyly and anterior expansion of posterior genes. (A,C) Normal forelimb (A) and hindlimb (C) bud at E12.5 with five digits; (B,D) Ift88^hypo forelimb (B) and hindlimb (D) bud at E12.5 show polydactyly. Arrowheads indicate digit condensations. (E) Fgf4 is normally expressed in the posterior AER; (F) Fgf4 is expressed in the entire AER of Ift88^hypo mutant limb bud at E10.5. (G,I) Hoxd11 (G) and Hoxd13 (I) are normally expressed in the posterodistal mesenchyme of E10.5 limb; (H,J) in Ift88^hypo mutants, Hoxd11 (H) and Hoxd13 (J) expression is expanded anteriorly and proximally. Green and red arrowheads in E-J indicate the anterior boundary of the AER in wild-type and Ift88^hypo limbs, respectively.