Fig. 3. Xc-Myc knockdown impairs endothelial cell development. (A,B) Whole mount in situ hybridization (stage 37) for endothelial lineage marker X-msr; (B) enlargement of the embryos shown in A. X-msr staining is reduced and diffuse in Xc-Myc knockdown embryos throughout, and the vitelline vein network (vvn), aortic arches (aa), tunica vasculosa lentis (tvl), anterior cardinal vein (acv) and rostral lymph sac (RLS) are reduced or missing. H, heart; pcv, posterior cardinal vein; isv, intersegmental vessels. (C) Histology of posterior cardinal vein (pcv) and dorsal aorta at stage 37. Uninj, uninjected control; Xc-Myc Mo, Xc-Myc morpholino-injected embryos. The vessels found in Xc-Myc morpholino-injected embryos have remarkably thin walls and empty lumens. Analyses based on five or six embryos from two different experiments.