Expression of Lpa4 mRNA in some blood vessels. (A-G) In situ hybridization of Lpa4 mRNA. The antisense probe was used in panels A,C-E,G. A positive signal was present in the peripheral vasculatures but not in the large blood vessels (C, upper right). In panels B,F, the sense probe was hybridized to serial sections of A and E, respectively, as negative controls. Little or no signal was observed. Nuclei were counterstained with Kernechtrot. (H) Immunohistochemistry for VWF counterstained with Mayer's hematoxylin. This was a serial section of panel G. Panels A-D,G-H were tissue sections from embryos at E18.5, while panels E-F were from embryos at E12.5. Lpa4 mRNA expression can be seen in the peripheral vasculatures of the tongue (A), heart (C), muscle (D), lung (E), and kidney (G). Scale bars, 200 μm in panels A-F and 50 μm in panels G,H.