Depletion of syntaxins in the early Caenorhabditis elegans embryo reveals a pole for membrane fusion events in cytokinesis

Background: During cytokinesis, the plasma membrane of the parent cell is r esolved into the two plasma membranes of the daughter cells. Membrane fusio n events mediated by the machinery that participates in intracellular vesic le trafficking might contribute to this process. Two classes of molecules t hat are required for membrane fusion are the t-SNAREs and the v-SNAREs. The t-SNAREs (syntaxins) comprise a multi-gene family that has been suggested to mediate, at least in part, selective membrane fusion events in the cell. Results: We have analyzed the genome of Caenorhabditis elegans and identifi ed eight syntaxin genes. RNA-mediated interference (RNAi) was used to produ ce embryos deficient in individual syntaxins and these embryos were phenoty pically characterized. Embryos deficient in one syntaxin, Syn-4, became mul tinucleate because of defects in karyomere fusion and cytokinesis. Syn-4, l ocalized both to ingressing cleavage furrows and to punctate structures sur rounding nuclei as they reformed during interphase. Conclusions: Our analyses indicate; that both cytokinesis and reformation o f the nuclear envelope are dependent on SNARE-mediated membrane fusion.