Establishment of Anterior–Posterior Axis in the Mouse Embryo

Abstract

The anterior–posterior (A–P) axis is the first established and morphologically discernible axis of the body during mouse development. From embryonic day (E) 4.5 to E6.5 of mouse embryos, the formation of the distal visceral endoderm (DVE) followed by that of the anterior visceral endoderm (AVE) breaks the A–P symmetry of the embryo. The DVE progenitor cells arise in primitive endoderm (PrE) cells of the late blastocyst with an asymmetrical distribution. This asymmetry may contribute to the determination of the A–P axis in later embryos. At E5.5, DVE cells mature, and migrate from the distal tip to the future anterior side. The DVE migration guides the migration of newly formed AVE and trigger the extensive movement of visceral endoderm (VE) cells in a wide area. Our observations revise the earlier model about AVE development, namely, that the AVE is directly derived from the DVE.