Hox Genes are Differentially Expressed during Mouse Placentation

Abstract

The placenta is an extraembryonic tissue that is formed between mother and fetus and mediates delivery of nutrients and oxygen from the mother to the fetus. Because of its essential role in sustaining the growth of the fetus during gestation, defects in its development and function frequently result in fetal growth retardation or intrauterine death, depending on its severity. Vertebrate Hox genes are well known transcription factors that are essential for the proper organization of the body plan during embryogenesis. However, certain Hox genes have been known to be expressed in placenta, implying that Hox genes not only play a crucial role during embryonic patterning but also play an important role in placental development. So far, there has been no report that shows the expression pattern of the whole Hox genes during placentation. In this study, therefore, we investigated the Hox gene expression pattern in mouse placenta, from day 10.5 to 18.5 of gestation using real-time RT-PCR method. In general, the 5" posterior Hox genes were expressed more in the developing placenta compared to the 3" Hox genes. Statistical analysis revealed that the expression of 15 Hox genes (Hoxa9, -a11, -a13/ -b8, -b9/ -c6, -c9, -c13/ -d1, -d3, -d8, -d9, -d10, -d11, -d12) were significantly changed in the course of gestation. The majority of these genes showed highest expression at gestational day 10.5, suggesting their possible role in the early stage during placental development.