Identification of monoclonal nonspecific suppressor factor beta (MNSF beta) as one of the genes differentially expressed at implantation sites compared to interimplantation sites in the mouse uterus

Successful implantation requires synchronous development of and active dial ogue between the maternal endometrium and the implanting blastocyst. While it is well established that appropriate maternal steroid hormones are essen tial for endometrial preparation for implantation, the molecular events at the actual site of implantation are still little understood. The aims of ou r studies were to identify genes explicitly expressed or repressed at the s ites of implantation by utilising RNA differential display (DDPCR), and to establish the roles of these genes in the implantation process in a mouse m odel. Ten bands unique in implantation sites compared to interimplantation sites were identified by DDPCR and subsequently confirmed by Northern blott ing. One of these bands contained a cDNA fragment that was highly homologou s to mouse monoclonal nonspecific suppressor factor beta (MNSF beta) or Fau . The full cDNA sequence of this gene, obtained by screening a lambda gt11 cDNA library, was essentially the same as MNSF beta, except that it had muc h longer 5' untranslated region. Interestingly, both Northern and immunohis tochemical analysis showed that the expression of this gene was much lower in implantation sites compared to interimplantation sites on day 4.5 of pre gnancy, when embryos first attach to the uterus and initiate implantation, and on day 5.5, when implantation has advanced. These results suggest a rol e for MNSF during implantation and early pregnancy, possibly through regula ting the proliferation and/or differentiation of uterine stromal cells. It may also be involved in the selective production of TH2-type cytokines in i mplantation sites to regulate the immune system at the maternal-fetal inter face. Mol. Reprod. Dev. 55:351-363, 2000. (C) 2000 Wiley-Liss, Inc.