Fig. 7: Unsynapsed X segments are transcriptionally active.

A Mid-pachytene nuclei of wild-type and YBT7 genotypes stained with DAPI (blue), anti-RNAPII (green), and anti-SYP-4 (red). Scale bar = 3 μM. n = 42 and 73 nuclei for WT and YBT7, respectively. B Distribution of the percentages of wild-type and YBT7 early and mid-pachytene nuclei with a chromosome stained for SYP-4 but not RNAPII (black), one or more chromosomes lacking SYP-4 and RNAPII staining (yellow), all chromosomes stained with SYP-4 and RNAPII (light blue), and one or more chromosome stained without SYP-4 and with RNAPII (blue). Possible interpretations for the different categories are illustrated on the bars: In wild type, the synapsed chromosome that does not stain with RNAPII is probably chromosome X, and in YBT7 these are the synapsed X segments (black). In YBT7, the chromosomes without SYP-4 and RNAPII are segments of the X that are not synapsed and are silent (yellow). Nuclei that only contain chromosomes with SYP-4 and RNAPII have either lost the internal segment or both segments are synapsed and active (light blue). The chromosomes that stain with RNAPII but not with SYP-4 are the internal segments that cannot synapse and that escape both sex chromosome silencing and MSUC (blue). C Mid-pachytene nuclei stained with DAPI (blue), anti-RNAPII (green), anti-SYP-1 (red), and anti-HIM-8 (white). n = 30 nuclei. D Mid-pachytene nuclei stained with DAPI (blue), anti-RNAPII (green), anti-SYP-4 (red), and left linc-20 (white). n = 27 and 40 nuclei for WT and YBT7, respectively. E Mid-pachytene nuclei stained with DAPI (blue), anti-RNAPII (green), anti-SYP-4 (red), and X left FISH probe (white). Dashed lines: HIM-8 or FISH marked body n = 21 and 47 nuclei for him-8 and YBT97, respectively. Scale bar = 3 μM.