[
EXS,
1993]
Receptors for acetylcholine are present in nematodes. Studies using physiological and biochemical methods have revealed the existence of nicotinic acetylcholine receptors with a novel pharmacology. Caenorhabditis elegans provides a particularly suitable organism with which to investigate such receptors using molecular genetic approaches. Mutants resistant to the cholinergic agonist (and anthelmintic drug) levamisole have permitted the isolation of a number of genes, including structural subunits of the nicotinic acetylcholine receptor. The only known viable mutants of nicotinic receptors are those of Caenorhabditis elegans. This organism offers the prospect of studying the developmental and regulatory effects of the loss of a single component of the receptor. Using Caenorhabditis elegans it is possible to select interesting phenotypic mutations by in vivo mutagenesis before determining the causative lesion. Resistance genes other than those encoding structural subunits are of particular interest, as they will encode additional polypeptides closely associated with nicotinic receptor function. Such proteins are often difficult or impossible to identify using conventional biochemical approaches, whereas genetic selection should permit their identification.
[
Mech Ageing Dev,
2001]
The nematode Caenorhabditis elegans has become a model system for the study of the genetic basis of aging. In particular, many mutations that extend life span have been identified in this organism. When loss-of-function mutations in a gene lead to life span extension, it is a necessary conclusion that the gene normally limits life span in the wild type. The effect of a given mutation depends on a number of environmental and genetic conditions. For example, the combination of two mutations can result in additive, synergistic, subtractive, or epistatic effects on life span. Valuable insight into the processes that determine life span can be obtained from such genetic analyses, especially when interpreted with caution, and when molecular information about the interacting genes is available. Thus, genetic and molecular analyses have implicated several genes classes (dnf, clk and eat) in life span determination and ha iie indicated that aging is affected by alteration of several biological processes, namely dormancy, physiological rates, food intake, and reproduction.