Mapping vertebrate embryos

A major challenge in embryology is to understand how cells become specialized into distinct lineages and assembled into a pattern of tissues that will make up the embryo. The discovery that patterns of gene expression are conserved among embryos of the favourite vertebrate species for laboratory study — zebrafish, frog (Xenopus), chick and mouse — has led to a surge of interest in finding out how similar development is in these embryos. This primer describes the organization of the body plan in the embryos of these four species. We will look at their ‘fate maps’, which are drawn by tracing the tissues that develop from particular regions of the early embryo and so can be used to predict the normal developmental fate of cells.