Abstract. The homeobox genes expressed in highly invasive murine hemochorial placentae and in non-invasive caprine epitheliochorial/syndesmochorial placentae were surveyed by cloning and sequencing RT-PCR products generated by using sets of degenerate primers. All HOX9 paralogues, i. e., HOXA-9 -HOXD-9, were expressed both in the murine and in the caprine placenta. Among the non-clustered HOX genes, the placental expression of EMX2 and ATBF1 was newly demonstrated in the present study. In the murine placenta, Hoxa-10 was the dominant homeobox gene expressed. In the intercotyledon region of the caprine placenta, HOXA-10 was expressed at a low level, while HOXB-7 transcript levels were high. By contrast, no Hoxb-7 expression was found in the murine placenta. The high HOXB-7 mRNA levels in the caprine placenta might represent the expression in the allantois which enormously expands in the caprine epitheliochorial/ syndesmochorial placenta. Despite the difference in the pattern of HOXA-10 and HOXB-7 expression, the homeobox genes expressed in two morphologically and functionally different types of placentae were surprisingly similar with each other. In the mouse plcenta, the expression levels of Hoxa-9, Emx2, Msx2 and ATBF1 did not show any consistent changes during the pregnancy period examined. Hoxb-9 expression levels exhibited a decline between Day 13 and Day 15 of pregnancy, while the expression levels of Hoxc-9 and Hoxd-9 gradually increased from Day 13 to Day 19. The Hoxc-9 expression level reached to the maximum level on Day 19. The functional significance of these homeobox genes remains to be clarified.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.