Jpx utilizes a trans mechanism to activate Xist expression in Tg(Jpx) mice.

(A) RNA FISH (left column) and corresponding DNA FISH (two columns on the right) in wildtype and Tg(Jpx) transgenic mEFs. Representative images shown of ectopic expression patterns observed in cells. Probes are described in Fig 1A. For RNA: Jpx (red, Cy3) and Xist (green, FITC). For DNA: Jpx+Xist (red, Cy3) and Rnf12 (green, FITC). Right column: DNA FISH with two probes to distinguish the endogenous X chromosomal locus (overlapping red and green) from the transgenic insertion site (red only). Closed arrowhead: endogenous RNA transcripts (RNA FISH) and the endogenous X chromosomal loci (DNA FISH). Open arrowhead: transgenic RNA transcripts and the transgenic integration site. Scale bar: 5μm. (B) Percentage of cells with Jpx or Xist expression categorized by the number of RNA clouds detected. (C) Percentage of endogenous versus transgenic Jpx clouds counted in Tg(Jpx) mEFs.