FIG. 3.

Expression of YY1 protein in wild-type murine preimplantation embryos. Immunofluorescent detection of YY1 protein was performed on wild-type preimplantation embryos by confocal microscopy. Embryos were stained with monoclonal and polyclonal (not shown) anti-YY1 antibodies and polyclonal anti-TBP and anti-Sp1 antibodies. The leftmost column represents embryos stained with these primary antibodies and visualized with FITC-conjugated secondary antibodies. The middle column represents the same embryos stained with propidium iodide that visualizes DNA. The rightmost column shows superimposed images of the antibody and DNA staining. (A to C) YY1 expression in a one-cell unfertilized oocyte; (D to F) TBP expression in a one-cell unfertilized oocyte; (G to I) YY1 expression in a one-cell fertilized embryo; (J to L) YY1 expression in a two-cell embryo. Note the pronounced YY1 expression in the nucleus as shown by the intense yellow signal as a result of the colocalization of the YY1 signal (green) and the DNA signal (red) (L). (M to O) YY1 expression in the inner cell mass and trophoblast of an E3.5 blastocyst; (P to R) Sp1 expression in the nucleus of a blastocyst. Note the intense yellow signal as a result of colocalization of the Sp1 signal (green) with DNA signal (red) (R).