In the hindbrain, Wnt can directly (not shown) or indirectly (via Meis3) induce the expression of the Hox1–Hox5 paralog group genes. In addition, FGF signaling alone or in concert with RA signaling can further refine the expression pattern of Hox genes in the anterior and posterior hindbrain, respectively. In the spinal cord, Wnt-induced Cdx 1/2/4 expression leads to the induction of the Hox6-Hox13 paralog group genes. Moreover, RA signaling alone or in combination with FGF signaling can further refine the expression, directly or indirectly (via Cdx1), of Hox genes in the anterior and posterior spinal cord, respectively.