6 Genetics of Cell Lineage

Abstract

I. INTRODUCTION
Why isolate Caenorhabditis elegans mutants that are abnormal in cell lineage? A biochemist might answer, “To identify molecules involved in generating particular patterns of cell divisions or in specifying particular developmental fates.” A physiologist might answer, “To obtain individuals lacking particular cells, so as to help assign functional roles to those cells” (or, conversely, “to obtain individuals with particular functional—or developmental—defects, so as to identify those cells normally needed for those functions”). And a geneticist might answer, “To define the logic of the network of genetic interactions and to examine in vivo the effects of perturbing individual molecular elements of that network.” Of course, mutants offer approaches toward all of these goals.

Many cell-lineage mutants of C. elegans have been isolated and characterized in detail both developmentally and genetically. The complete knowledge of the cellular anatomy and cell lineage of C. elegans (see Chapters 4 and 5 and Appendixes 1–3) has allowed the definition of developmental defects at the level of resolution of single cells. The small size of this animal, as well as its rapid life cycle, self-fertilizing nature, and ease of handling have made sophisticated genetic manipulations possible (see Chapter 2).

In this chapter, we describe some of the methods underlying and conclusions derived from studies of the genetics of C. elegans cell lineage. Rather than presenting a comprehensive catalog of the approximately 50 known genes with characterized effects on cell lineage (such information is available from the references cited in Appendix 4)...