In the next five years, molecular biology will get its first look at the complete genetic code of a multicellular animal. The Caenorhabditis elegans genome sequencing project, a collaboration between Robert Waterston's group in St. Louis and John Sulston's group in Cambridge, is currently on schedule towards its goal of obtaining the complete sequence of this organism and all its estimated 15,000 to 20,000 genes by 1998. By that time, we should also know the complete genome sequence of a few other organisms as well, including the prokaryote Escherichia coli and the single-celled eukaryote Saccharomyces
[
Methods Cell Biol,
1995]
Complementary DNA libraries are useful tools for uncovering genes of interest in C. elegans and finding specific homologies to genes in other organisms (Waterston et al., 1992; McCombie et al., 1992). When working with existing cDNA libraries, be sure to carefully choose which libraries would be most beneficial to the type of research being done. Some libraries may be specific for genes that are present in lower copy numbers, whereas others may be of a more general nature. It is important to fully understand the source and construction of the library you will be working with. Once an appropriate library has been chosen, work may begin to isolate a specific cDNA and sequence it completely or to survey many cDNAs by single-pass DNA sequencing. Whatever the project, it is important to develop a specific strategy for both the sequencing and the organization of the clones being characterized. The strategies and procedures we have outlined in this chapter have proven effective for rapid and comprehensive cDNA characterization.
[
1987]
Since the last review in this series [Johnson, 1985], many papers have appeared dealing directly with the aging process in both Caenorhabditis elegans and Turbatrix aceti. We will review this work and also briefly review other areas of C. elegans research that may impact on the study of aging. C. elegans has become a major biological model; four "News" articles in Science [Lewin, 1984a,b; Marx, 1984a,b] and inclusion as one of three developmental genetics models in a recent text [Wilkins, 1986] indicate its importance. Recent work has verified earlier results and has advanced progress toward new goals, such as routine molecular cloning. The aging studies reviewed here, together with new findings from other areas of C. elegans research, lay the groundwork for rapid advances in our understanding of aging in nematodes. Several areas of research in C. elegans have been reviewed recently: the genetic approach to understanding the cell lineage [Sternberg and Horvitz, 1984] and a brief summary of cell lineage mutants [Hedgecock, 1985]. The specification of neuronal development and neural connectivity has been a continuing theme in C. elegans research and reviews of these areas have also appeared [Chalfie, 1984; White, 1985]. A major genetic advance is the development of reliable, if not routine, mosaic analysis [Herman, 1984; Herman and Kari, 1985], which is useful for the genetic analysis of tissue-limited gene expression. Hodgkin [1985] reviews studies on a series of mutants involved in the specification of sex. These include her mutations that cause XO worms (normally males) to develop as hermaphrodites and tra mutations that change XX hermaphrodites into phenotypic males. The work on the structure and development of nematode muscle has been summarized by Waterston and Francis [1985]. A comprehensive review of aging research, containing useful reference material on potential biomarkers, has appeared [Johnson and Simpson, 1985], as well as a review including