[
Seminars in Developmental Biology,
1994]
Gastrulation in Caenorhabditis elegans has been described by following the movements of individual nuclei in living embryos by Nomarski microscopy. Gastrulation starts in the 26-cell stage when the two gut precursors, Ea and Ep, move into the blastocoele. The migration of Ea and Ep does not depend on interactions with specific neighboring cells and appears to rely on the earlier fate specification of the E lineage. In particular, the long cell cycle length of Ea and Ep appears important for gastrulation. Later in embryogenesis, the precursors to the germline, muscle and pharynx join the E descendants in the interior. As in other organisms, the movement of gastrulation permit novel cell contacts that are important for the specification of certain cell fates.
[
Methods Mol Biol,
2000]
The complete description of its nearly invariant cell lineage and the growing availability of cloned genes and markers for the cell lineage make Caenorhabditis elegans particularly favorable for mosaic analysis, and the literature is rich in examples that prove the usefulness of this approach. Because genetic mosaic analysis in C. elegans has recently been reviewed by Herman who developed many of the techniques, this review will be more concerned with the recent technical advances rather than with an extensive background of the approach. First we shall present a brief summary of the principles of mosaic analysis as it is typically performed in C. elegans. This will be followed by a description of markers that indicate mosaicism and by a discussion of a hypothetical analysis of an essential gene.