Identification of novel genetic markers for mouse yolk sac cells by using microarray analyses

The mouse embryonic yolk sac consists of a visceral yolk sac (VYS) and parietal yolk sac (PYS), and may function as a materno-fetal exchange system for nutrients, waste and gas, and physical protector for the embryo/fetus. The present study was undertaken to characterize gene expression of the VYS and PYS endodermal cells, and to identify their novel genetic markers from microarray data with RT-PCR and in situ hybridization analyses. As a result, Apoa4, Lrp2, Fxyd2, Slc34a3 and Entpd2 were selected as genetic markers of VYS epithelial cells. These markers were predominantly expressed in VYS epithelial cells, and may involve nutrient uptake and transport of various substances across the VYS membrane. Gkn2 and Pga5 were selected as markers for PYS cells. Gkn2 might be involved in the migration of PYS cells on Reichert’s membrane. Pga5 belongs to the aspartic proteinase family, and is known as ”pepsinogen F.” It may act on degradation of maternal proteins for the nutrient supply to the fetus. The present study also indicated that Mmp1a and Prl7b1 can be used as markers for placenta tissue. The markers reported may be useful for characterization of murine extraembryonic tissues, including yolk sacs and placenta, during development and in culture. Gene expression of the VYS, PYS (endodermal cells and Reichert’s membrane), placenta, liver and small intestine at E12.5 was examined. The numbers of each organ examined are 3, 3, 2, 2 and 1 for the VYS, PYS, placenta, liver and small intestine, respectively.