H3K4 erasure in mes-4 primordial germ cells (PGCs) is normal, but exhibits precocious reappearance. H3K4me2 staining in (A-C) early and (B-D) late stage primordial germ cells (PGCs of embryos from (A,C) wild type, (B,D) mes-4(bn85) and (C,E) mes-2 mothers. DAPI, red; H5, green; PGL-1, blue in merged images. In the lower panels, PGCs (boxed; arrows) are enlarged, and the H3K4me2 staining is shown in grayscale (left). Arrows mark PGCs.