Fig. 1. Expression of PKI in chick embryos. Whole-mount in situ hybridization with a PKI probe. (A,C,E,G) Dorsal views of chick embryos from stages 4 to 8. (B,D,F,H) Close-ups of Hensen’s node. (I,J) Stage 10+ and stage 16 embryos. At stage 4 (A,B), expression is uniform on both sides of the node and primitive streak. At stage 6 (C,D), expression becomes stronger in the right side of the node. The right-handed expression at the node continues through stage 7+ (E,F). Black and white arrowheads indicate the areas where PKI signal is asymmetric. PKI seems symmetrically expressed in the head process, head fold and emerging somites at these stages. At stage 8 (G,H), expression at the node becomes symmetric. At stage 10+ (I) and 16 (J), PKI is expressed at the notochord, somites, heart (h) and branchial arch (b).