Identification of Heterochronic Mutants in Caenorhabditis elegans: Temporal Misexpression of a Collagen::Green Fluorescent Protein Fusion Gene

• Published in: Genetics (Austin) Vol. 149; no. 3; pp. 1335 - 1351
• Main Authors: Abrahante, Juan E, Miller, Eric A, Rougvie, Ann E
• Format: Journal Article
• Language: English
• Published: United States Genetics Soc America 01-07-1998
• Subjects: Animals; Animals, Genetically Modified; Caenorhabditis elegans - cytology; Caenorhabditis elegans - genetics; Caenorhabditis elegans - physiology; Collagen - biosynthesis; Crosses, Genetic; Ethyl Methanesulfonate; Gamma Rays; Gene Rearrangement; Genes, Helminth; Genetic Complementation Test; Genetic Linkage; Green Fluorescent Proteins; Kinetics; Luminescent Proteins - biosynthesis; Mutagenesis; Recombinant Fusion Proteins - biosynthesis; Time Factors
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/149.3.1335

The heterochronic genes lin-4, lin-14, lin-28, and lin-29 specify the timing of lateral hypodermal seam cell terminal differentiation in Caenorhabditis elegans. We devised a screen to identify additional genes involved in this developmental timing mechanism based on identification of mutants that exhibit temporal misexpression from the col-19 promoter, a downstream target of the heterochronic gene pathway. We fused the col-19 promoter to the green fluorescent protein gene (gfp) and demonstrated that hypodermal expression of the fusion gene is adult-specific in wild-type animals and temporally regulated by the heterochronic gene pathway. We generated a transgenic strain in which the col-19::gfp fusion construct is not expressed because of mutation of lin-4, which prevents seam cell terminal differentiation. We have identified and characterized 26 mutations that restore col-19::gfp expression in the lin-4 mutant background. Most of the mutations also restore other aspects of the seam cell terminal differentiation program that are defective in lin-4 mutant animals. Twelve mutations are alleles of three previously identified genes known to be required for proper timing of hypodermal terminal differentiation. Among these are four new alleles of lin-42, a heterochronic gene for which a single allele had been described previously. Two mutations define a new gene, lin-58. When separated from lin-4, the lin-58 mutations cause precocious seam cell terminal differentiation and thus define a new member of the heterochronic gene pathway.