Fig. 1.

H3K9me3 signal enrichment persists on pericentric heterochromatin throughout germ cell development upon extended tissue fixation. a Immunofluorescent analysis of H3K9me3 (green) in cryosections of E10.5 and E11.5 trunks containing germ cells and of E13.5 male and female gonads using the regular fixation protocol. H3K9me3 staining is present in DAPI (blue)-dense regions of E10.5 PGCs and somatic cells. At E11.5 H3K9me3 transiently disappears from pericentric heterochromatin of E11.5 PGCs only. Thereafter, H3K9me3 returns in E13.5 DAPI-dense regions. b Using extended fixation, H3K9me3 is retained in DAPI-dense regions of PGCs and somatic cells in all embryonic stages examined. E10.5 and E11.5 germ cells are marked with OCT4 (red), while E13.5 germ cells are marked with TRA98 (red). Using regular or extended fixation, two embryos or gonads were analysed per stage, and at least 20 PGC nuclei were recorded. Representative germ cells are marked with yellow dashed circles. Scale bars represent 5 μm