Fig. 1. PH-GFP binds to plasma membrane PtdIns(4,5)P₂ in mouse oocytes. Confocal images of GFP fluorescence in the equatorial plane of mouse MII oocytes, acquired 2-3 hours after injection with the cRNA encoding PH-GFP (A,B) or the mutant PH(R40L)-GFP, which does not bind to PtdIns(4,5)P₂ (C). Corresponding line intensity profiles are displayed on the right, with GFP fluorescence expressed as relative fluorescence units (F) and bright field images shown on the left. (A) MII oocyte with the animal pole out of focus (fluorescence from the chromosomes, stained with Hoechst 33342, was captured in a plane above and superimposed). (B) MII oocyte with the animal pole in the focal plane. Note the higher fluorescence intensity associated with the plasma membrane in the vegetal pole. (C) MII oocyte expressing PH(R40L)-GFP. For each condition, similar patterns of staining were obtained in at least 20 oocytes. Bar, 10 µm.