Involvement of EAT/mcl-1, a bcl-2 related gene, in the apoptotic mechanisms underlying human placental development and maintenance

The EAT/mcl-1 gene was isolated during the early differentiation of a retinoic acid-induced human embryonal carcinoma cell line to the trophectoderm lineage. EAT/mcl-1, a bcl-2 related gene, is involved in the genetic pathway of apoptosis; this suggests a role for apoptosis and the involvement of this gene in early placental development. In the current investigation, we analysed expression of EAT/mcl-1 at the mRNA level by Northern blot analysis and in situ hybridization, as well as at the protein level, by immunoblot analysis and immunohistochemistry. Our results identified constant expression of this gene in the placenta throughout pregnancy as well as a shift in its localization from the cytotrophoblast in the first trimester to the syncytiotrophoblast in the third trimester. In addition, there was an inverse correlation between EAT/mcl-1 expression and TaT-mediated deoxyuridine triphosphate nick-end labelling (TUNEL) reactivity in trophoblasts in the first trimester. These results suggest a role for EAT/mcl-1 in both early placental development in regulating trophoblast differentiation as well as a role for this gene in placental maintenance in regulating the process of trophoblast turnover.