Figure 2.

H3K9 tri-methylation patterns in oocytes and zygotes. In both mouse (a, a'-c, c') and sheep (d, d'-f, f'), GV-stage oocytes (a, d), MII-stage oocytes (b, e) and zygotes (c, f) were stained for H3K9 tri-methylation (m3-H3K9, green). The samples were counterstained with propidium iodide (PI, red) to visualize the DNA. In both species, the nucleus (a, d) or chromosomes (b, e) of oocytes were heavily stained for m3-H3K9. In zygotes (c and f), two parental pronuclei were asymmetrically stained for m3-H3K9, which the paternal pronucleus showed no or feint staining (arrow).