Worm Breeder's Gazette 11(3): 56
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.
Behavioral mutants have been useful in studying the function and development of the C. elegans nervous system. We're using this behavioral genetic approach to study the 79 neurons specific to the male. On the assumption that these additional neurons mediate mating behavior, which is seen in males but not hermaphrodites, we have been screening for mutant strains defective in this behavior using the screen first described by Hodgkin (Gen. 103:43-64, 1983). him-5( e1490) worms are mutagenized with EMS; 20 P0 L4 hermaphrodites are cloned; 10 F1 worms are picked per mutagenized P0; and 10 F2 L4 hermaphrodites are cloned per P0 and their male progeny tested for mating efficiency via a qualitative mating test (6 males x 6 unc-52 hermaphrodites). Mutations that would reduce mating efficiency in a non-specific manner (such as Uncs, Dpys, Lons) are discarded. Those strains that appear morphologically normal under the dissecting scope yet fail to mate or mate at a very low efficiency (1-5% cross progeny compared to wild type) are screened under Nomarski optics for defects in male reproductive structures. Thus far,we have screened 2,123 haploid genomes. Although the clonal nature of this screen is designed to pick up behavioral (i.e. neural) defects, screening by mating efficiency will of course also pick up mutants defective in male copulatory structures. This is a welcome side effect as we are also interested in genes that affect the development of the copulatory structures - particularly the spicules (see below; Chamberlin & Sternberg, WBG 11(2) :103). Wild type males normally respond to a hermaphrodite by backing along the length of the hermaphrodite with its tail in contact (avoiding the head and tail of the hermaphrodite by turning either under or over the hermaphrodite body near but before it reaches the ends) until it locates the vulva. At this point the male stops, slides back and forth until it inserts its spicules into the vulva and finally injects sperm. To date, we have backcrossed nineteen strains (about a 25% success rate) which appear to be wild type in morphology yet are unable to perform the normal mating behavior. We call these strains Cod for copulation defective (or Celibate old dullards). sy155, sy166, sy172, and sy178 males respond only weakly to a hermaphrodite if at all. Three mutants, sy35, sy174, and sy181, are unable to turn normally around the head and tail of the hermaphrodite (backing all the way to the tip and stopping or turning unsuccessfully). Two of the turning defective mutants, sy174 and sy181, plus sy157, are unable to locate the vulva. Eight mutants, sy38, sy43, sy153, sy156, sy158, sy165, sy176, and sy177, are unable to insert their spicules. And lastly, three mutants, sy36, sy179, and sy180, appear to mate normally but sire very few or no progeny. Since the hermaphrodite brood sizes are normal in these strains, they appear to be defective in sperm transfer. So far, we have characterized twelve mating defective mutants with morphological defects. Mutations that disrupt gonad, ray, and/or spicule development have been isolated due to the reduced male mating efficiency phenotype they confer. The gonads of sy189 males exhibit abnormal linker cell migration and failure to attach to the cloaca. Four mutations, sy31, sy68, sy173, and sy183, affect ray formation. sy183 causes variably swollen rays and tail structures. sy31 causes a swollen ray, Ram phenotype (ray morphology, Scott Baird, personal communication), but does not affect the spicules. sy68 males have crumpled spicules and also retain the larval tail spike, usually at the expense of rays 7-9. sy173 males lack rays 1-6, have posterior alae, and wrinkled spicules. This mutation maps to LGIII and fails to complement mab-5(e1239) for the ray and spicule abnormality. Four other mutations also cause crumpled or wrinkled spicules: bx31, sy29, sy32, and sy66. Most of these are pleiotropic in their phenotype. bx31 hermaphrodites are variably Muv. bx31 maps to the left arm of LGII and fails to complement lin-31(n301) for both the vulval and the spicule phenotype. sy29 hermaphrodites are Vul, and sy66 worms, both males and hermaphrodites, are notch-head Vab. Only sy32 exhibits no pleiotropies at the plate level. bx31, sy29, sy32, and sy66 all exhibit defects in the B cell (spicule) lineage (work in progress). Three mutations, sy170, sy187, and sy188 result in spicules that appear to be normal except that they lack the autofluorescent properties of wild-type spicules, and they are extremely flexible. If a male with one of these mutations extrudes his spicules, they flatten out and 'flap in the breeze'. Finally, one mutation, sy182, results in the absence of male progeny despite the him-5(e1490) background of the parental strain. We are currently characterizing sy182 in order to determine the nature of this phenotype. Special thanks to Scott Baird and Scott Emmons for bx31 and to Gregg Jongeward for the title.