Fluorescence in situ hybridisation on RNA analysis of X-linked gene expression in XEN compared to TS female cells. (A) Representative images of fluorescence in situ hybridisation on RNA (RNA-FISH) analysis in extraendoderm stem (XEN) female cells (GHP7/9 cell line). The inactive X chromosome is identified through Xist RNA accumulation (green). Primary transcription at the indicated X-linked gene is codetected in red. Scale bar = 5 μm. (B) Cumulative histograms of the percentages of nuclei with the depicted expression pattern are shown. X-linked genes are grouped according to their H3K27me3 class. [K27-high], Enriched in H3K27me3 in female compared to male XEN cells; [K27-low], Low levels of H3K27me3 in female and in male XEN cells. On the left of the histogram, the diagram shows the localisation of RNA-FISH probes along the X chromosome. n > 200. (C) The same types of data shown in (A) are given for female trophoblast stem (TS) cells (F3 cell line). (D) The same types of data shown in (B) are given for female TS cells. *P < 0.05 by Χ2 test for significant differences with expression profiles in XEN cells (n > 200).