The C-elegans septin genes, unc-59 and unc-61, are required for normal postembryonic cytokineses and morphogenesis but have no essential function in embryogenesis

Septins have been shown to play important roles in cytokinesis in diverse o rganisms ranging from yeast to mammals, In this study, we show that both th e unc-59 and unc-61 loci encode Caenouhabditis elegans septins, Genomic dat abase searches indicate that unc-59 and unc-61 are probably the only septin genes in the C. elegans genome. UNC-59 and UNC-61 localize to the leading edge of cleavage furrows and eventually reside at the midbody, Analysis of unc-59 and unc-61 mutants revealed that each septin requires the presence o f the other for localization to the cytokinetic furrow. Surprisingly, unc-5 9 and unc-61 mutants generally have normal embryonic development; however, defects were observed in post-embryonic development affecting the morphogen esis of the vulva, male tail, gonad, and sensory neurons. These defects can be at least partially attributed to failures in post-embryonic cytokineses although our data also suggest other possible roles for septins, unc-59 an d unc-61 double mutants show similar defects to each of the single mutants.