Examining Viability and Parental Contributions in a Spindle Assembly Mutant in C. elegans

Schimmel/Conrades Science Center Atrium

Cell division is a highly conserved process that must be precisely regulated. To better understand cell division, we are characterizing mutations in a gene in C. elegans that is required for cell division. Mutant early embryos fail to form bipolar mitotic spindles. Because of this defect in spindle assembly, we call this gene sas-X. Most of the previous work in the Hamill lab has used a temperature-sensitive allele of sas-x called or452ts. In our work reported here, we focused on two newly generated sas-x alleles, or1942 and or2000. Our three primary goals included determining the hatching rate for embryos produced by homozygous mutant animals, investigating the phenotype of these embryos, and establishing if the defect was passed through the egg, sperm, or both. or1942 mutant worms produced all dead embryos. In contrast to or452ts alleles, embryos from or1942 worms show failures in cell division but not during the first two cell cycles. or2000 mutants are often sterile, but when embryos are produced they are inviable with early cell division defects. These phenotypic differences likely reflect the distinct nature of the alleles. To test parental requirements we generated homozygous mutant males and attempted to cross them into wild-type females. Crosses with or452ts males showed nearly a 50% reduction in embryo viability suggesting a partial paternal contribution. Surprisingly, we found that both or1942 and or2000 males have defective mating structures and are incapable of mating. We believe that characterization of this mutant will provide important insights into the process of mitotic spindle assembly and cell division.