Bex1, a gene with increased expression in parthenogenetic embryos, is a member of a novel gene family on the mouse X chromosome

Parthenogenetic and normal blastocysts were compared using differential dis play analysis as a means to identify new imprinted genes, A single gene was identified with increased expression in parthenogenetic blastocysts, sugge sting it might be an imprinted gene expressed from the maternally inherited allele, The gene, named Bex1 (brain expressed X-linked gene), maps near Pi p on the mouse X chromosome and to Xq22 in humans. Database homology search es revealed two additional uncharacterized cDNAs similar to Bex1 that were named Bex2 and Bex3. Allele-specific expression analysis of Bex1 using Fl b lastocysts indicated an excess of transcript expressed from the maternally inherited allele compared with the paternally inherited allele, This excess level of transcript derived from the maternally inherited allele may be du e to imprinted X inactivation of the paternally inherited allele in the ext raembryonic lineages of female embryos rather than a result of genomic impr inting.