Expression of ARIA during mouse embryogenesis. (A) Whole-mount in situ hybridization of ARIA in e9.5d mouse embryo. ARIA was expressed in blood vessels during embryogenesis as indicated by arrows (ARIA-AS). Negative control using sense cRNA probe (ARIA-S) did not show significant signals. In situ hybridization of TIE-2, expressed almost exclusively in endothelial cells and early hematopoietic cells, was performed for a positive control of the blood vessel expression. (B) Sections of embryo from the whole-mount in situ hybridization. ARIA expression was observed in intersomitic arteries, dorsal aorta (black arrows), and blood vessels on the yolk sac (white arrows). (Scale bars, 100 μm.) (C) Relative expression of ARIA in the whole embryos at indicated embryonic day.