A novel X gene with a widely transcribed Y-linked homologue escapes X-inactivation in mouse and human.
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.
Department of Obstetrics and Gynecology, University of Tennessee, Memphis 38103.
A I
AI
Agulnik
M J
MJ
Mitchell
M G
MG
Mattei
G
G
Borsani
P A
PA
Avner
J L
JL
Lerner
C E
CE
Bishop
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000032:analysis; D005260:Female; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D008540:Meiosis; D051379:Mice / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D014960:X Chromosome; D014998:Y Chromosome
D017931:DNA Primers; D018076:DNA, Complementary