The homeobox genes MSX2 and MOX2 are candidates for regulating epithelial-mesenchymal cell interactions in the human placenta

Homeobox genes of the Msx and Mox families are coexpressed in the vertebrat e embryo in regions of epithelial-mesenchymal interactions. Here we show th at a member of each family is expressed in extra-embryonic structures where epithelial and mesenchymal cell layers contact. In situ hybridization stud ies on first trimester human placental sections reveal that MSX2. and MOX2 are expressed predominantly in the cytotrophoblast cell layer. In term plac enta, MSX2 and MOX2 are expressed in the syncytiotrophoblast. This is the f irst study to describe the expression of MOX2 in human tissues and to show that members of the Msx and Mox families of homeobox genes are expressed wh ere epithelial and mesenchymal cell layers contact in the human placenta. A combinatorial code of homeobox genes that includes members of the Msx, Mox and Dlx families has been predicted to regulate epithelial-mesenchymal cel l interactions in the vertebrate embryo. We have shown that MSX2, MOX2, DLX 4 and the HB24 homeobox gene are expressed in the epithelial and mesenchyma l cell types that form the placenta. We predict that this combination of ho meobox genes is involved in regulating epithelial-mesenchymal cell interact ions in extraembryonic tissues. (C) 2000 IFPA and Harcourt Publishers Ltd.