Worm Breeder's Gazette 14(1): 25 (October 1, 1995)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The typical eukaryotic genome harbors many families of transposable elements. The movement of these elements within a genome is regulated by factors as diverse as: genetic background, cell type, developmental stage, copy number, temperature, nutritional status and "genomic stress". This spectrum implies that a variety of regulatory mechanisms converge to control transposon activity. However, we know very little about what mechanisms, if any, might regulate transposition genome-wide in response to these diverse signals.
Five active transposon families have been characterized in C. elegans, designated Tc1-Tc5. All five families are regulated by a common factor, the mut-2 mutator [defined by the mutation mut-2(r459)]. In fact, three of these elements, Tc3, Tc4 and Tc5, are genetically active only in this mut-2 mutant background. In addition to highlighting the existence of factors with broad regulatory roles, the mut-2 mutator has been a cornerstone of transposon tagging and reverse genetic approaches in the worm. To understand how it functions to control transposition, and to make it an even more useful tool in C. elegans research, we are mapping (and ultimately cloning) mut-2. Using Tc1 activity as an assay, Finney and Horvitz mapped a mutator activity in the mut-2 mutant strain TR674 to the unc-13 region of LGI. However, it is unclear whether these experiments mapped the mut-2 mutator or a Bergerac mutator (Tc1-specific) present in the strain in which mut-2(r459) was isolated. Using an assay specific for mut-2, reversion of unc-22::Tc4 and unc-22::Tc5 alleles, we have confirmed that the mutator in question was indeed mut-2. We crossed TR674 [mut-2(r459);unc-54(r323::Tc1)] by TW195 [dpy-5(e61)] -- see map in WBG. Of 59 Dpy, Unc recombinants, three were homozygous mut-2(r459), based on the following: (1) they revert to unc-54+ at high frequency; (2) when Dpy, Mut, non-Unc revertants were crossed by unc-22::Tc4 and unc-22::Tc5 mutants, nearly all the resulting Dpy twitchers yielded non-twitcher revertants at high frequency (18/19 for unc-22::Tc4 and 22/23 for unc-22::Tc5). These results confirm that the mut-2 mutator maps to the dpy-5;unc-13 region and provide a strain with a convenient visible marker linked to mut-2(r459). This strain, TW404 [genotype dpy-5(e61);mut-2(r459)] will be very useful in further mapping studies that are in progress. It may also be useful for others who wish to manipulate the mutator background for their purposes.