A 450 kb transgene displays properties of the mammalian X-inactivation center.
X inactivation results in inactivation of one X chromosome to compensate for gene dosage differences between mammalian females and males. It requires the X-inactivation center (Xic) and Xist in cis. We report that introducing 450 kb of murine Xic/Xist sequences onto autosomes activates female dosage compensation in male ES cells. Xist is induced upon differentiation and can be expressed from both endogenous and ectopic loci, suggesting that elements for counting and choosing Xs are present in the transgene. Differentiating transgenic ES cells undergo excessive cell death. Postnatally, Xist is expressed only from the transgene. Ectopic Xist RNA structurally associates with the autosome and may inactivate a marker gene in cis. These results argue that the Xic is contained within 450 kb and that these sequences are sufficient for chromosome counting, choosing, and initiation of X inactivation.
Lee
J T
JT
Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142, USA.
Strauss
W M
WM
Dausman
J A
JA
Jaenisch
R
R
D000818:Animals; D001483:Base Sequence; D016923:Cell Death / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002678:Chimera; D004303:Dosage Compensation, Genetic; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D015870:Gene Expression / Q000235:genetics; D005816:Genetic Complementation Test; D005819:Genetic Markers; D017404:In Situ Hybridization, Fluorescence; D007763:Lac Operon; D008297:Male; D008322:Mammals; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D012313:RNA / Q000378:metabolism; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D013234:Stem Cells / Q000166:cytology / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*; D019076:Transgenes / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics*
D005819:Genetic Markers; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D014157:Transcription Factors; C077885:XIST non-coding RNA; D012313:RNA