Fig. 2. Receptor trafficking-defects in dab2 mutant VE. Immunohistochemistry and immunofluorescence on E6.5 embryos. (A-D) Dab2 immunostaining. Dab2 protein was detected in the VE of control embryos (A), at the apical surface as well as associated with both EEA1-positive and negative vesicles (A',B). Absence of Dab2 staining was used to identify dab2^-/- embryos (C-D). EEA1 positive vesicles were reduced in mutant embryos (D). (E-H) Megalin immunostaining. Megalin was detected at the apical surface and associated with EEA1-positive vesicles in control embryos (E-F). In dab2^-/- VE (G-H), megalin protein was restricted to the apical surface and little intracellular protein or colocalization with EEA1 was detectable (G-H). (I-L) Cubilin immunostaining. Cubilin was detected in the apical brush-border and in vesicles within the apical and basolateral cytoplasm of control embryos (I-J). In dab2^-/- embryos, cubilin was retained at the apical membrane and was not detected in vesicles (K-L). Bars, 40 µm (A); 10 µm (A',B). A, apical; BL, basolateral; (+/), dab2^+/+ or dab2^+/–.