The Cdc42/MRCK/myosin II pathway is activated in the FC. (A) Immunofluorescence detection of activated myosin II (P-MRLC) in a fertilized oocyte. Images are z-compressions across the entire zygote volume, for 3D renditions, highlighting the FC. (B) Detection of Cdc42·GTP in the FC. The image shows a fertilized oocyte expressing the Cdc42·GTP biosensor MCB-EGFP. The oocyte was fertilized in vitro after zona pellucida removal. (C) Immunofluorescence detection of MRCKβ in a fertilized oocyte. Images are z-compressions across the entire zygote volume, for 3D renditions, highlighting the FC. (D) Immunofluorescence detection of activated myosin II (P-MRLC) and MRCKβ in a fertilized oocyte. Fluorescence intensity profiles in B and D correspond to the cortical regions delineated by the gray arrowheads in the merge images. F-actin was labeled with Alexa Fluor 568–phalloidin. Chromosomes were stained with TO-PRO-3 (magenta). Sp: sperm chromatin. Scale bars are 10 µm.