Fig. 9

Pericentromeres are more frequently found as single units in PGCs compared to the somatic cells. a Nuclear spread preparations were immunostained for CREST (yellow) and H4K20me3 (green). At E10.5, many small-sized chromocenters [identified by DAPI (blue) density and enrichment of H4K20me3) and their corresponding CREST signals can be observed in the PGCs (E10.5 and E11.5 germ cells were identified by OCT4 (red) and E13.5 germ cells with TRA98 (red)]. Examples of pericentric regions containing a single CREST focus are indicated by arrowheads. This pattern of dispersed pericentric heterochromatin organization in germ cells, as opposed to the clustering of pericentric heterochromatin regions and associated centromeres in somatic cells, is observed at least until E13.5. Representative germ cells are marked with yellow dashed circles. Three or more embryo trunks or gonads were pooled for the nuclear spread preparations and 20–30 PGC, and somatic nuclei were recorded. Scale bars represent 10 μm. b Frequency distribution of the number of pericentric heterochromatin regions (defined by delineation of the H4K20me4 areas) containing a specific number of CREST signals as indicated on the X axis. Asterisks (*, **, *** or ****) indicate significant differences