Fig. 7. Cx431 expression in a PEO explant. A 24 hour PEO explant culture (A) is comprised of a monolayer of cells with epithelial morphology. These cells express cytokeratin (B) and Cx431 (C). Punctate Cx431 immunolabeling is found in abundance along regions of cell-cell contact (arrows in C). In many cells, the Cx431 immunostaining occupied much of the peripheral cell membrane, outlining the polygonal shape of the proepicardial cells (C). By contrast, Cx431 immunolabeling is absent in proepicardial cells from a Cx431 knockout mouse embryo (D). Scale bars: 200 µm in A; 80 µm in B-D.