Status of H3K27me3 enrichment and XIST-RNA accumulation on the inactive-X in distantly related mammals.

<p><b>A</b>. Examples of immunofluorescence for H3K27me3 (in green) on elephant cells (left panel), tammar wallaby cells (centre) and opossum cells (right panel). The top row shows a representative nucleus from female cell, the bottom row from male cell. Arrow heads point the inactive X chromosome enriched in H3K27me3. n = 100. <b>B</b>. Example of RNA FISH showing accumulation of <i>XIST</i> transcripts (in grey) on the DAPI-dense inactive X chromosome of female elephant cells. <b>C</b>. Immunofluorescence for H3K27me3 (in green) combined with RNA FISH for the <i>UBE1</i> primary transcripts (in red) in female cells from tammar wallaby. Arrow head points the inactive X chromosome containing <i>UBE1</i> transcripts and enriched in H3K27me3. Asterisk shows <i>UBE1</i> transcripts from the active X chromosome. n = 30. <b>D</b>. Dual immunofluorescence for H3K27me3 (in green) and H3S10ph (in red) on female tammar wallaby cells showing that enrichment in H3K27me3 (arrow heads) on the Xi is restricted to the G1/S phase and the early G2 phase of the cell cycle. n = 90. <b>E</b>. Immunofluorescence for H3K27me3 (in green) combined with a cell proliferation assay to label replicating DNA (in red) showing H3K27me3 enrichment on the Xi in late S phase, at the time of Xi replication (enrichment of H3K27me3 (green) on the replicating Xi (red)). n = 200. DAPI is shown in grey. Scale bar = 1 µm.