Fate-mapping, the tagging of specific cells or tissues in an embryo, and following their movements and development over time, has a long history as a valuable method. The earliest fate-maps date back to the 1880’s. The first “modern” fate-maps were created in 1929 by Walter Vogt, who applied vital dyes to regions of the amphibian embryo. This allowed him to track which embryonic regions developed into which adult tissues. Two methods, featured in the December issue of CSH Protocols and freely available to non-subscribers, present new fate-mapping techniques, which overcome some serious experimental barriers.
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The first, from Rusty Lansford and colleagues, describes Ex Ovo Electroporation of DNA Vectors into Pre-gastrulation Avian Embryos. The technique allows the incorporation of fluorescent proteins into cells at earlier stages than previous methods, thus allowing one to follow cell movements through important early events such as gastrulation. Growing the embryos ex ovo instead of in ovo allows for easier orientation and manipulation of the embryo and more precise control over the timing of development.

The second featured method, Fate-Mapping Technique: Using Carbocyanine Dyes for Vital Labeling of Cells in Gastrula-Stage Mouse Embryos Cultured In Vitro, is part of a set of three fate mapping protocols from Patrick Tam’s lab. The obvious problem with fate-mapping in the mouse is that the embryo is not easily accessible, as it develops inside the mother. Tam’s lab has developed methods to tag cells in the early mouse embryo with vital dyes, with grafts of fluorescently labeled cells, and via electroporation of DNA constructs. The key to the success of the methods is that they don’t significantly perturb normal development, at least that seen for the mouse in Roller Culture.