Worm Breeder's Gazette 9(1): 33
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.
Vulval development involves six precursor cells, P3.p-P8.p, each of which has the potential to express any one of three cell lineages, designated the 1 , 2 and 3 lineages. A regulatory cell, the anchor cell, controls the expression of these lineages. Homeotic mutations have been identified that cause some of the Pn.p cells to adopt fates normally characteristic of other Pn.p cells. Mutations in genes such as lin-2 and lin-10 result in a Vulvaless phenotype caused by the expression of 3 lineages by cells that would otherwise undergo 1 or 2 lineages. The Multivulva phenotype caused by mutations in genes such as lin-15 is the result of the transformation of 3 lineages to 1 or 2 lineages. Finally, mutations in lin-31 result in the uncontrolled expression of 1 , 2 and 3 lineages such that the same Pn.p cell in different animals can express any of the three lineages. Genes such as these may be involved in anchor cell signaling or in the subsequent determination of Pn.p cell lineage. We are initiating a molecular analysis of the determination of vulval cell lineages by seeking clones containing the genes described above. One way to clone genes that have been identified only genetically is to induce mutations with a transposon. John Collins and Phil Anderson (personal communication) have isolated mutant strains (e.g. TR679), derived from Bristol Bergerac hybrids, that appear likely to have a high frequency of transposition of the transposon Tc1. From TR679, we have isolated 26 putative transposon- induced mutations in five genes that affect the determination of vulval precursor cell fates: lin-2, lin-12, s of the mutations in the genes lin-10 and lin-12 has been the most extensive. lin-12 has been previously isolated as a molecular clone (Iva Greenwald, personal communication) and our genomic blotting studies indicate that our new lin-12 allele differs from the wild-type allele by the insertion of a Tc1 transposon. This result provides direct evidence that TR679- induced mutations can be caused by Tc1 insertion and thus encourages us to attempt to isolate other lin genes as molecular clones by transposon-tagging in TR679. In general, we plan to isolate transposon-tagged genes by identifying a Tc1 copy that has inserted within the gene. In the case of our new TR679-induced lin-10 allele, unlinked Tc1 copies were removed by repeatedly backcrossing the mutant strain with N2. Next, recombinants between lin-10 and two closely linked markers, dpy-5 and unc-29, were isolated. Genomic blotting analysis of these recombinants revealed two Tc1 copies that were inseparable from the lin-10 mutation. These Tc1 copies are located within 0.2 map units to the left and 0.07 map units to the right of lin-10. Presumably, at least one of these copies lies within the lin-10 gene. Similar analyses for the TR679-induced lin-2, s are in progress.