The embryonic lethal mutation zyg-10(b261) is an allele of the atx-2 gene and disrupts multiple aspects of early embryogenesis

The <i>zyg-10 ( b261 )</i> mutation was identified in one of the earliest screens for temperature-sensitive embryonic lethal mutations in <i>C. elegans</i> , but the cytological defects underlying the embryonic lethal phenotype, as well as the molecular identity of <i>zyg-10</i> had not been previously established. Here we show that <i>zyg-10 ( b261 )</i> is an allele of the <i>atx-2</i> (ataxin-related) gene and that embryos produced by <i>atx-2 ( b261 )</i> mothers exhibit a variety of defects including eggshell defects, cytokinesis failure, spindle mispositioning, and chromosome missegregation. We also show that the localization of separase, a regulator of egg-shell formation and mitosis, is defective in <i>atx-2 ( b261 )</i> embryos.