Figure 7.

Transition in the spatial expression pattern of the genes encoding Hox target transcription factors associated with cartilage differentiation and changes in the Hox13dKO autopod. Dorsal view of gene expression detected by in situ hybridization in the forelimb bud at (a, f, k, p) approximately E10.5, (b, c, g, h, l, m, q, r) E11.5 and (d, e, i, j, n, o, s, t) E12.5. (a) In wild‐type embryos, Aff3 was expressed throughout the entire limb bud mesenchyme excluding the narrow distal most region at E10.5. Aff3 expression was not found in the autopod at (b) E11.5; however, at (d) E12.5 expression was detected in the cells in/around the perichondrium of the autopod but not in the interdigital mesenchyme. In Hox13dKO embryos, Aff3 expression expanded to the proximal autopodal region (c) at E11.5 then the expression was observed throughout the entire autopodal mesenchyme (e) at E12.5. Bnc2 expression was not detected in the (f) E10.5 mesenchyme but was detected in the center of the stylopod and zeugopod (g) at E11.5. (i) Bnc2 expression was later found in the perichondrium of the limb cartilage including the autopod at E12.5. Bnc2 expression was expanded to the proximal Hox13dKO autopod (h) at E11.5 and throughout the entire mesenchyme (j) at E12.5. Nfib expression was found in the proximal region of the (k) E10.5 limb bud then in the zeugopod/autopod boundary region at (l) E11.5. (n) Nfib expression was detected in the perichondrium of the autopodal cartilage at E12.5. In the Hox13dKO limb bud, expression was detected throughout the entire autopodal mesenchyme both (m) at E11.5 and (o) E12.5. Runx1t1 expression was detected in the proximal center of the (p) E10.5 and (q) E11.5 limb but excluded from the autopodal region. (s) In the E12.5 autopod, Runx1t1 expression was detected in the cartilaginous condensation. In Hox13dKO embryos, Runx1t1 expression was expanded to the proximal autopod at (r) E11.5 and the central region of the autopod showed expression at (t) E12.5