Fig. 1. Expression of Odd1 in the chick embryo. (A,B) Whole-mount in situ hybridization for Odd1 in HH Stage 5 (A) and Stage 9 (B) chick embryos. (C,D) In situ hybridization for Pax2 at Stage 9 (C) and Stage 11 (D). Note that Odd1 is expressed earlier than Pax2, and that it extends more broadly than Pax2 in lateral, anterior and posterior directions. Arrows in A and C indicate nascent Odd1 and Pax2 expression, respectively. (E-G) Sections of whole-mount in situ hybridization for Odd1. At Stage 11 (E) Odd1 is expressed in the intermediate mesoderm and extends into the lateral plate but is not found in the nephric duct. At Stage 13 (F), Odd1 is expressed in mesenchymal cells adjacent to mesonephric tubules and also in splanchnic mesoderm derivatives, including the dorsal mesentery, but not in epithelialized nephric duct or tubules. At embryonic day 5 (G), Odd1 is expressed in the coelomic lining (arrowhead) and in the rudimentary somatic gonad (arrow). (H-M) Expression of Odd1 and Pax2 protein during formation of the nephric duct rudiment. At Stage 9 (H-J), before the duct rudiment is morphologically detectable, most Pax2-expressing cells (arrow) also express Odd1. Inset in J shows merged detail from I and J. By Stage 10 (K-M), the nephric duct rudiment has begun to bulge dorsally (arrow) and continues to express Pax2 but no longer expresses Odd1. Inset in M shows merged detail from L and M. (N-P) In the developing mesonephros, Odd1 protein is expressed in mesenchymal cells adjacent to the tubules, but not in the Pax2-expressing tubules themselves. Inset in P shows merged detail from O and P. d, nephric duct; im, intermediate mesoderm; lp, lateral plate; n, Hensen's node; t, tubules.