Abstract
The discovery of the embryonic organizer by Hilde Mangold and Hans Spemann in 1924 was one of the most ground-breaking achievements in the 1900 century for developmental biologists and beyond. Ever since the organizer was first described in newts, developmental biologists have been trying to uncover similar structures in other organisms. While the Spemann-Mangold organizer as an axis-inducing centre is evolutionary conserved in vertebrates, similar organizing centres have yet to be observed in mammals. In this review, we will provide a brief historical overview of the discovery of the mouse gastrula organizer and discuss its potential as an organizer throughout early post-implantation mouse development. We discuss cell migrations through the mouse organizer region and morphogenesis of organizer cells and tissues. Finally, we examine the evidence arguing for and against the existence of a head organizer in mice, and the role of the anterior visceral endoderm and the prechordal plate in organizing head structures.