H3K36me2 is distributed in heterochromatin in mouse preimplantation embryos. Localization of H3K36me2 in mouse preimplantation embryos at various stages. Embryos were fixed and stained with anti-H3K36me2 (red), anti-H3K9me3 (green), and DAPI (blue). (A) Images of single optical sections. Low-power views of merged images, maintaining consistent contrast settings across different stages, are displayed on the left. Magnified views of indicated nuclei, with individual contrast adjustments to compare the localization patterns, are shown on the right. TE, trophectoderm; ICM, inner cell mass. (B) Pearson correlation coefficients of DNA and H3K36me2 (top) or H3K9me3 (bottom). The number of nuclei (n) and P values, calculated using the Mann–Whitney U test and Hommel correction to the four-cell stage, are shown. See Fig. 1 legend for the details of box plots. Scale bars, 10 μm.