Comparative analysis of HOXC-9 gene expression in murine hemochorial and caprine synepitheliochorial placentae by in situ hybridization

Mammalian placentae exhibit wide structural diversity among different speci es and are formed under intricate interplay between the embryonic trophobla st and the maternal endometrial cells. Increasing evidence in the literatur e indicates a possible role played by homeobox genes in the complex placent al organogenesis. Although the expression of all HOX 9 paralogs has been de monstrated both in highly invasive murine hemochorial placentae and in non- invasive caprine synepitheliochorial placentae, no reports so far published in the literature described the patterns of gene expression of Hoxc-9 in t he murine nor those of HOXC-9 in the caprine placenta at cellular levels. W e carried out comparative analyses of the location and identity of the cell s expressing Hoxc-9/HOXC-9 during various stages of placentation in the mur ine hemochorial and caprine synepitheliochorial placentae by means of in si tu hybridization using murine Hoxc-9 or caprine HOXC-9 cRNA probe, respecti vely. The results demonstrated that Hoxc-9 mRNA was expressed at high level s in giant trophoblast cells of murine placentae on Days 12-19, but not on Day 8. Similar analysis of caprine Day 75 and Day 100 placentae revealed th at the binucleate trophoblast cells that penetrate the uterine luminal epit helial cell layer, strongly expressed HOXC-9 mRNA. Although the functional significance of Hoxc-9/ HOXC-9 gene expression in trophoblast cells remains to be elucidated, it was suggested that it might play a role in the regula tion of invasiveness or endocrine activities in the murine giant trophoblas t cells and/or the caprine binucleate trophoblast cells. Anat Rec 259:383-3 94, 2000. (C) 2000 Wiley-Liss, Inc.