Figure 4.

In situ RNA and murine X whole chromosome library detection in AS-2B mouse/human hybrid cells that contain both an active human and mouse X chromosome. Both human and murine Xist RNA is expressed from these chromosomes as a result of 5azadC treatment. (A and B) The difference between the reactivated murine Xist RNA and human XIST RNA is illustrated in these cells, with the murine RNA appearing highly localized (red) and the human XIST RNA (green) showing a focus of expression (most likely representing the site of transcription) with particles that drift away into the nucleoplasm. Reactivated murine Xist RNA localizes to the active X chromosome (C–E). (C) The murine Xist RNA (red) is discretely contained in the hybrid cell nucleus (D) in a pattern similar to the murine X chromosome signal (green; the mouse X chromosome library cross-reacts slightly with the human X chromosome, giving a second green signal apparent in the middle cell in D); (E) the murine Xist RNA colocalizes with the active murine X chromosome (overlap is yellow).Figure 5. The mouse X chromosome painted by the Xist RNA does not inactivate. Codetection of murine Xist RNA (green) and Zfx RNA or Pgk1 RNA (red) in undenatured 1B-5C-3B cells. (A and B) Zfx RNA (red) is expressed from cells that also express mouse Xist RNA (green); (C) Pgk1 RNA expression (red) is also expressed from chromosomes that express Xist RNA (green), suggesting that the active X chromosome is not inactivated as a result of Xist localization. Expression of mouse genes appears to be unaffected in cells that express mouse Xist. (A) There is a similar pattern and intensity of expression of Zfx RNA in cells that express mouse Xist (top), and those that do not (bottom). (C). Similarly, there is comparable Pgk1 expression in cells that express mouse Xist (left) and cells that do not (far right).