Worm Breeder's Gazette 9(1): 44
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.
Dominant conditional embryonic-lethal mutations could identify haplo- insufficient genes whose product levels are important for pattern formation. Dominants could also identify genes that would not be found in screens for recessive lethal mutations, such as members of multi-gene families in which one member can substitute for another. They could also identify (probably less interesting) genes for proteins in complexes that can be inactivated by presence of a defective subunit. We are isolating dominant temperature-sensitive embryonic lethals, by mutagenizing worms with EMS and cloning Fl progeny at 16 . After the worms have laid eggs, they are shifted to 25 , removed the next day, and their eggs are scored for hatching one day later. From screens of approximately 3000 Fl animals so far, we have isolated six mutants and begun to characterize them. All carry dominant, maternal-effect mutations that cause all progeny of heterozygous mutant hermaphrodites to die as embryos. One is leaky; a few progeny embryos hatch but then arrest as L1's. Only one is fertile as a homozygote at 16 . The others are inviable or sterile, indicating that the corresponding genes have a zygotic as well as a maternal function. The temperature-sensitive periods of embryos from heterozygous hermaphrodites vary from near the time of fertilization to late in embryogenesis. We are more precisely defining the temperature-sensitive periods of these mutants as well as analyzing their defective phenotypes by Nomarski microscopy. We are also initiating gene-dosage experiments to determine whether the mutations cause change in or loss of function of mutant gene products. Meanwhile, we are continuing to isolate more dominant-lethal mutations.