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Updated: Jun 9, 2026

Combined DNA-RNA Fluorescent In situ Hybridization (FISH) to Study X Chromosome Inactivation in Differentiated Female Mouse Embryonic Stem Cells
Published on: June 14, 2014
A novel X gene with a widely transcribed Y-linked homologue escapes X-inactivation in mouse and human
A I Agulnik1, M J Mitchell, M G Mattei
1Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38103.
Abstract:
A new gene, designated Smcx, was cloned from the mouse X chromosome by its homology to the Y located gene Smcy. Using direct in situ hybridisation Smcx was mapped to the distal end of the mouse X chromosome (XF2-XF4) and its human homologue, SMCX, was mapped to proximal Xp (Xp11.1-Xp11.2). Further meiotic mapping in the mouse placed Smcx in the Plp-Pdha1 interval. As Smcx/SMCX have widely expressed homologues on the Y chromosome, they appeared good candidates for genes that escape X-inactivation. In the human we show this to be the case as SMCX is expressed in hamster-human hybrids containing either an active or inactive human X chromosome. Two alleles of Smcx were found to be expressed in T(16;X)16H female mice despite the intact X chromosome being inactive in all cells. This indicates that Smcx is also not subject to X-inactivation and provides the first example of a gene that is expressed from inactive and active X chromosomes in the mouse.
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