A LIMITED NUMBER OF CAENORHABDITIS-ELEGANS GENES ARE READILY MUTABLE TO DOMINANT, TEMPERATURE-SENSITIVE MATERNAL-EFFECT EMBRYONIC LETHALITY

Dominant gain-of-function mutations can give unique insights into the study of gene function. In addition, gain-of-function mutations, unlik e loss-of-function alleles, are not biased against the identification of genetically redundant loci. To identify novel genetic functions act ive during Caenorhabditis elegans embryogenesis, we have collected a s et of dominant temperature-sensitive maternal-effect embryonic lethal mutations. In a previous screen, we isolated eight such mutations, dis tributed among six genes. In the present study, we describe eight new dominant mutations that identify only three additional genes, yielding a total of 16 dominant mutations found in nine genes. Therefore, it a ppears that a limited number of C. elegans genes mutate to this phenot ype at appreciable frequencies. Five of the genes that we identified b y dominant mutations have loss-of-function alleles. Two of these genes may lack loss-of-function phenotypes, indicating that they are noness ential and so may represent redundant loci. Loss-of-function mutations of three other genes are associated with recessive lethality, indicat ing nonredundancy.