Fig. 4. Composite image of RT-PCR analysis of occludin TM4^- isoform expression in different species using primer sets shown in Table 1. Both TM4⁺ and TM4^- isoforms are detectable in African Green Monkey (AGM) BSC1 epithelial cells but only the canonical TM4⁺ isoform is detectable in mouse tissues, cells and embryos, and in canine-derived MDCK cells. B, embryo blastocyst stage; BS, AGM BSC1 cells; CM, CMT64/61 cells; K, kidney; L, liver; M, marker lane; MK, MDCK cells; Mo, embryo morula stage.