SCML2 suppresses PRC1-mediated H2AK119ub but promotes PRC2-mediated H3K27me3 on pericentromeric heterochromatin. (A) Immunostaining of testicular paraffin sections with the indicated antibodies. All images were acquired with a confocal microscope. Boxed regions are magnified in the right panels. Scale bars: 20 µm (left) and 5 µm (right). SCML2 suppresses H2AK119ub on pericentromeric heterochromatin (PCH), shown by arrows. (B) Quantification of relative signal intensity of H2AK119ub on PCH in pachytene spermatocytes. The relative intensity is a ratio of mean signal intensity on PCH to mean signal intensity of a given nucleus after the subtraction of background signal intensity (see Materials and Methods). Wild-type: 123 regions of PCH were quantified in 41 cells from three mice; Scml2-KO: 93 regions of PCH were quantified in 31 cells from three mice. Mean±s.e.m. (error bars); ***P<0.0001, unpaired t-test. (C) Immunostaining of H3K27me3 and SYCP3, a marker of chromosome axes, in chromosome spreads of each substage of pachytene and diplotene spermatocytes. Dashed circles, sex chromosomes; arrows, PCH in wild type. Images were acquired with a wide-field microscope. Scale bars: 10 µm. (D) Summary of the action of SCML2 on PCH in male germ cells.