Fig. 1. Spatiotemporal expressions of Hoxa13 (A-E) and Hoxa13 protein (F) during posterior GGU/tail development. (A) Stage 10 [arrow indicates caudal intestinal portal (CIP)]. (B) Stage 14 (arrow indicates CIP). (C) Stage 17 (long arrows show tail tip and hindgut, arrowheads at tail gut). C1 and C2 note planes of cryosection. (C1) Hoxa13 endodermal expression in the cloaca (Cl). (D) Expression in tail and posterior hindlimb bud (red arrows) at stage 22. (E) Dissected E4 posterior gut. Expression is present in the hindgut (HG) and cloacal (CL) endoderm and cloacal mesoderm, no expression is detected in the ceca (CE) or midgut (MG). (F) Protein expression in hindgut endoderm (endo.), arrow, at E6.