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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 VIIIFuture Directions

Several themes have emerged from the study of cell migration and axon guidance in C. elegans. First, a few global directional cues orient cells and pioneer growth cones along the natural axes of the hypodermal and pharyngeal epithelia, and local path or target cues provide further specificity and fidelity. Second, substrate and direction of movement, and motility itself, are determined by the surface receptors and cytoskeletal adaptors expressed within each cell. Third, hormones and growth factors acting through conserved signal transduction pathways can regulate the navigational program, including gene expression and cytoskeletal responses.

From the perspective of both cell and developmental biology, many basic questions remain unanswered. What are the directional cues for anterior and posterior migrations? How are the circumferential positions of longitudinal axon tracts specified? What is the arrangement of neuroglia and pioneers, and their molecular cues, in the developing nerve ring? How do various fasciculative cues act together to establish reproducible neighborhoods within axon tracts? What is the relationship, if any, between fasciculation and synapse formation? What is the basic mechanism of cell motility? How does activation of UNC-5 or other receptors cause cytoskeletal orientation? Most developmental problems can likely be solved by current methods, but understanding their cellular mechanisms may require new insights and techniques.

Finally, two outstanding technical developments deserve mention. First, transgenes expressing the reporter GFP allow the visualization of migrating cells and growth cones in living animals (Chalfie et al. 1994). Moreover, the dynamics of key proteins, including subcellular distribution and colocalization, during cell migrations can be studied by introduction of GFP modules into otherwise functional proteins. Second, the genome sequencing project has identified a cornucopia of adhesion molecules, cytoskeletal adaptors, and transcription factors (Sulston and al. 1992; Wilson et al. 1994; see Waterston et al., this volume) whose functions in development, and migrations in particular, can be explored by reverse genetics (Zwaal et al. 1993; Plasterk and Van Luenen, this volume).

Copyright © 1997, Cold Spring Harbor Laboratory Press.
Bookshelf ID: NBK20027
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