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Riddle DL, Blumenthal T, Meyer BJ, et al., editors. C. elegans II. 2nd edition. Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press; 1997.

Cover of C. elegans II

C. elegans II. 2nd edition.

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Section IIntroduction

During morphogenesis, some cells migrate from their origins to distant locations. The complex, stereotyped migrations of axonal growth cones, for example, determine the connectivity of the nervous system. Motile cells and processes can undergo directed movements in response to spatially patterned molecules (Keynes and Cook 1995; Garrity and Zipursky 1995), and recent studies suggest that specific directional cues are conserved from nematodes to chordates (Hedgecock et al. 1990; Ishii et al. 1992; Kennedy et al. 1994; Serafini et al. 1994; Colamarino and Tessier-Lavigne 1995).

Migrating cells may follow several different directional cues, often in strict sequence, during development. Moreover, they may halt migration at stereotyped positions or times either to divide or to differentiate. These changes in cell movements must reflect changes in the extracellular environment or changes within the motile cell itself. For example, cells might be constitutively responsive to multiple directional cues, changing course whenever they encounter a further cue within their repertoire. Instead, it appears that cells become responsive to new cues, or unresponsive to current ones, during the course of migration. Some transitions could be entirely autonomous, reflecting, for example, an intracellular clock, but many are contingent upon extracellular signals encountered during the course of migration. These transitions often involve new gene expression. Analysis of these transitions has identified signaling pathways and transcriptional cascades within migrating cells that help select substrate and direction of migration, or regulate transitions between motile and stationary states. One such pathway in nematodes responds to hormonal signals that advance developmental age throughout the larva, whereas others respond to growth factors that mark particular origins or migration paths. Together with cytoskeletal machinery for directed movement, these regulatory mechanisms form the intrinsic navigational programs of migrating cells.

This chapter reviews the developmental genetics of cell migration in Caenorhabditis elegans including growth cones and other motile cell processes. The origins and fates, including migrations and morphogenetic movements, of the somatic cells in both males and hermaphrodites have been traced in living embryos and larvae (Sulston and Horvitz 1977; Kimble and Hirsh 1979; Sulston et al. 1980, 1983). The cellular anatomy of the adult nervous system, including axon trajectories and synaptic connectivity, has been completely reconstructed from serial electron micrographs (Ward et al. 1975; Ware et al. 1975; Albertson and Thomson 1976; White et al. 1976, 1986; Hall and Russell 1991). Several earlier reviews of cell and growth cone migrations in C. elegans (Hedgecock et al. 1987; Wadsworth and Hedgecock 1992; Culotti 1994; Garriga and Stern 1994) and some recent general reviews of cell motility and pathfinding are highly recommended (Burns and Augustine 1995; Garrity and Zipursky 1995; Keynes and Cook 1995; Tanaka and Sabry 1995).

Copyright © 1997, Cold Spring Harbor Laboratory Press.
Bookshelf ID: NBK20190
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