Histone methylation dynamics on the paternal and maternal chromatin in the embryo.

<p>Immunostaining of dissected and fixed hermaphrodite gonads with antibodies specific to methylated histones (green) and DNA stained with DAPI (red). Before fertilization, oocytes are numbered with the −1 oocyte adjacent to the spermatheca. Polar bodies are denoted by ‘pb’, ‘mat’ is maternal, ‘pat’ is paternal. Scale bars represent 10 µm for all panels. <b>A</b>) H3K36me1 levels are high on both pronuclei after fertilization but absent on the paternal X chromosome, which is shown enlarged in the inset (top is merged image, bottom is H3K36me1 staining shown in grayscale). <b>B</b>) H4K20me1 is detectable as small foci on both pronuclei after fertilization with levels increasing on all chromosomes following oocyte meiosis. <b>C</b>) H3K79me2 levels are high on both pronuclei, low in 1 to 4-cell stage embryos, then high after the 16-cell stage. <b>D</b>) H3K79me3 is present on the maternal pronucleus but not the paternal after fertilization. Levels of H3K79me3 are very low after oocyte meiotic divisions and rise again after the 8-cell stage.