[
Results Probl Cell Differ,
1992]
Nematodes were first used to study embryogenesis more than 100 years ago, and this in part led to the concepts of cell-autonomous differentiation and localized cytoplasmic determinants. More recently, the techniques of genetics, experimental and descriptive embryology, and molecular biology have been combined to study the development of the small, free-living nematode Caenorhabditis elegans (Brenner 1974, 1988. This chapter focuses on embryonic development and is intended as a general overview of C. elegans embryogenesis, illustrating the experimental techniques available for this organism and the conclusions that can be drawn. Excellent reviews on postembryonic development (i.e. after hatching) in C. elegans and most other aspects of the worm's development, genetics and biology can be found in Wood (1988a). This book includes extensive appendices detailing techniques and anatomy and includes phenotypic descriptions of all mutants known at the time of publication. Other reviews of C. elegans embryogenesis can be found in Kemphues (1989), Wood (1988b), Schierenberg (1989) and Strome (1989).
[
ScientificWorldJournal,
2003]
We review key morphogenetic events that occur during Caenorhabditis elegans (www.wormbase.org/) embryogenesis. Morphogenesis transforms tissues from one shape into another through cell migrations and shape changes, often utilizing highly conserved actin-based contractile systems. Three major morphogenetic events occur during C. elegans embryogenesis: (1) dorsal intercalation, during which two rows of dorsal epidermal cells intercalate to form a single row; (2) ventral enclosure, where the dorsally located sheet of epidermal cells stretches to the ventral midline, encasing the embryo within a single epithelial sheet; and (3) elongation, during which actin-mediated contractions within the epithelial sheet lengthens the embryo. Here, we describe the known molecular players involved in each of these processes.
[
Seminars in Developmental Biology,
1992]
The cell lineage of the nematode Caenorhabditis elegans is essentially invariant and many cell fates are autonomous. It seems likely that factors capable of influencing lineage-specific gene expressions are segregated or activated asymmetrically during the early cleavages. The maternal genome provides most of the raw materials for embryogenesis as well as the information required to pattern early cell divisions. Nonetheless, the zygotic genome is transcriptionally active early in embryogenesis and is expressing at least some genes required for future developmental decisions. Several of these zygotically active genes have been analysed; they show complex lineal expression patterns, implying that their regulation may not be as straightforward as initially thought. However, an understanding of the logic governing how different combinations of transcription factors regulate lineage-specific differentiation may be possible in this organism.