Fig. 4. Differential expression of dab2 splice forms. (A) Schematics of the two alternatively spliced forms of dab2, p96 and p67. (B) Western blot analysis using a Dab2-specific antibody revealed differential expression of the two Dab2 protein forms in E6.5 embryos, embryoid bodies (EBs), kidney lysates and fibroblasts (MEF and NIH3T3). (C) Isoform-specific RT-PCR was performed to compare expression levels of p67 and p96 in embryos and cells. A common 5' PCR primer was used for both isoforms (a), together with a 3' primer that bridged the p67-specific splice junction (b) or that recognized the p96-specific exon (c). PCR was performed on serial threefold dilutions of cDNAs generated by RT-PCR from embryos and NIH3T3 cells. p67 mRNA levels were higher in an E7.5 embryo, whereas p96 mRNA levels were higher in NIH3T3 cells. PCR for gapdh was used as a control. (D) Immunofluorescence was used to visualize Dab2 protein in the VE of wild-type embryos at E6.5. Dab2 protein was both diffuse as well as vesicle-associated, at both the apical (A) and to as lesser extent the basolateral (BL) surface.