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. 2009 Mar 16;29(10):2748–2761. doi: 10.1128/MCB.01391-08

FIG. 1.

FIG. 1.

MEKK4 is expressed strongly in the trophoblast lineages of the developing placenta. MEKK4 was visualized in cryosections with anti-MEKK4 immunostaining (red) (A, C, D, H, and I) and by in situ hybridization with MEKK4 antisense probe (purple) (B, E, and F) or control MEKK4 sense probe (G). Nuclei were counterstained with DAPI (blue). (A) Anti-MEKK4 immunostaining shows that MEKK4 is expressed not only in the developing embryo but also in the invading primary giant cells lining the implantation site and the ectoplacental cone. (B) MEKK4 expression by in situ hybridization shows an identical expression pattern of MEKK4 message compared to the MEKK4 protein shown in panel A. (C and D) Strong MEKK4 expression in E8.5 chorion visualized by anti-MEKK4 immunostaining. The box indicates the area shown in the inset in panel D. (E) Strong expression of MEKK4 message in E8.5 chorion by in situ hybridization with antisense MEKK4 probe. (F) In situ hybridization with antisense MEKK4 probe in an E9.5 cryosection. (G) Control in situ hybridization with sense MEKK4 probe in an E9.5 cryosection. (H and I) Anti-MEKK4 immunostaining of E9.5 placenta (red). A white box indicates the area shown in the inset in panel I. For panels A to I, closed arrows indicate trophoblast giant cells, open arrows indicate spongiotrophoblasts, closed arrowheads indicate undifferentiated cuboidal trophoblasts, and open arrowheads indicate chorion. (J to O) Immunofluorescence microscopy of E9.5 placental cryosections stained with an anti-MEKK4 antibody (red) and counterstained with the nuclear stain DAPI (blue). (J to L) MEKK4 does not colocalize with PECAM-positive endothelial cells. Sections were also costained with anti-PECAM antibody (green). (M to O) MEKK4 colocalizes with cytokeratin (CK). Sections were also costained with anti-CK antibody. White boxes in panel J indicate the area that is enlarged in the insets in panels K and L. White boxes in panel M indicate areas enlarged in the insets in panels N and O. Filled arrowheads indicate MEKK4 in undifferentiated cuboidal trophoblasts. For panels J to O, filled arrows indicate PECAM-positive endothelial cells. Open arrows indicate sites with CK staining (green) having colocalization with MEKK4 (red). Bar, 100 μm.