Worm Breeder's Gazette 10(3): 102
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.
I have previously reported that the lectin wheat germ agglutinin and the monoclonal antibody Ab117 show specific binding to the vulva of adult hermaphrodites and the copulatory bursa of adult males (W.B.G. 10, #1, p. 117; Link, Ehrenfels, and Wood, Development 103, 485-495). Based on the observation that lin-22 males show strong ectopic binding of both WGA and Ab117, I devised a non-clonal screen to identify mutants that show ectopic WGA binding in hopes of identifying mutants with anterior/posterior transformation like lin-22. As described below, I have not yet identified mutants of this class, but have found a number of unexpected mutants interesting in their own right. Previously I visualized WGA or Ab117 binding to live animals using fluorescently-labeled lectin or secondary antibody. Because this method was not feasible for large scale mutant screening, I developed a peroxidase-coupled detection system that could be used with live animals and easily visualized under the dissecting microscope. Briefly, for visualizing WGA binding, animals were sequentially incubated in biotin-conjugated WGA and avidin-conjugated horseradish peroxidase, then developed using H2O2 and the chromogen 3-amino 9- ethylcarbazole. In order to use WGA binding in a non-clonal screen, I used semidominant mutations in her-1(n695 or y101) as the genetic background. These mutations variably masculinize XX animals, such that a sub-population of the adult animals (5-25%) are sufficiently somatically masculinized to show (lin-22 dependent) ectopic staining, but still retain a self-fertile hermaphrodite gonad. In three pilot experiments, I have screened approximately 60,000 EMS-mutagenized her- 1(n695) F2 adults and 20,000 EMS-mutagenized wild-type F2 adults for ectopic WGA binding, and have identified 15 independent mutations. These mutations, which fall into at least four complementation groups, appear to be unlike lin-22 in that their ectopic WGA binding is observed in both males and hermaphrodites. I have recently screened 500,000 EMS-mutagenized her-1(y101) F2 animals and identified an additional 50 independent (as yet uncharacterized) mutants. The most interesting of the characterized mutations are the allelic pleiotropic mutations ct109 and ct111(V). ct109 animals bind WGA and Ab117 over most of their cuticle surface. This surface binding is neither stage- nor sex-specific, although adult males show somewhat stronger posterior WGA binding than adult hermaphrodites. ct109 animals are uncoordinated and have improper body posture reminiscent of unc mutants known to have neurological defects. ct109 males have defective bursae, characterized by having crumpled spicules and abnormal rays. These males variably lack diagonal sex muscles. The most surprising ct109 phenotype is its ability to enhance the weak semidominant mutation lin-12(n302). Weak lin-12 dominant mutants such as n302 are Vul, while strong lin-12 dominant mutations such as n137 are Muv. lin-12(n302); imals closely resemble lin-12(n137); hermaphrodites have at least four pseudovulvae and males have ectopic hooks. All of the phenotypes observed for ct109 have also been observed for ct111, arguing that these phenotypes are likely to be the result of a single mutation. How can this motley collection of phenotypes be explained? A plausible explanation for the ct109 Unc and Mab phenotypes is that these animals are defective in cell-cell or cell-matrix interactions. Thus, the ct109 Unc phenotype might result from neuronal mis-wiring ( due to improper axon pathfinding) while the Mab phenotype might result from defects in migration of the sex muscle precursors and other bursal cells. To speculate wildly, perhaps ct109 defines a gene that modifies (glycosylates?) extracellular proteins or protein domains. This hypothetical modification would modulate cell-cell interactions in a manner akin to the way sialic acid addition modulates N-CAM function in vertebrates. This modification would also modulate the function of the lin-12 product (almost certainly a cell surface protein) and be involved in cuticle formation.