THE MURINE XE169 GENE ESCAPES X-INACTIVATION LIKE ITS HUMAN HOMOLOG

Among a number of genes that escape X-chromosome inactivation in human s, three have been evaluated in mice and unexpectedly all three are su bject to X-inactivation. We report here the cloning and expression stu dies of a novel mouse gene, Xe169, and show that it escapes X-inactiva tion like its human homologue. Xe169 was assigned to band F2/F3 on the mouse X chromosome by fluorescent in situ hybridization and Southern analysis indicates that the gene is located outside the pseudoautosoma l region. Homologous, but divergent, sequences exist on the Y chromoso me. In vitro and in vivo studies show that Xe169 is expressed from bot h the active and the inactive X chromosomes. Xe169 is the first cloned non-pseudoautosomal gene that escapes X-inactivaton in mice.