In wild-type 4-cell stage embryos, the APH-2 protein is associated with the surface membranes of all four cells. In
aph-1 mutant embryos, the APH-2 protein was mislocalized in all
aph-1 mutant embryos examined (n > 200 embryos between the 2-cell and 28-cell stages). In
aph-1 mutant embryos, APH-2 was not detectable on the cell surface, and was instead prominent in the cytoplasm of all four cells, where it was concentrated around the nucleus in a pattern characteristic of the endoplasmic reticulum. These results suggest that APH-1 facilitates the translocation of APH-2 to the cell surface.