Embryonic Cytokinesis in C. elegans
We have an ongoing study of chondroitin proteoglycans in C. elegans in collaboration with Karen Oegema’s group. A previous screen for C. elegans mutants defective in vulval invagination identified eight squashed vulva (sqv) genes. In sqv mutants, the vulval extracellular space fails to expand and the vulva appears collapsed. Stronger sqv mutations also show maternal effect lethality as a result of the inability of the progeny of homozygous mutants to initiate cytokinesis at the first cell division. Characterization of seven sqv genes showed they define components of the chondroitin biosynthesis pathway. A combination of biochemical purification, western blotting, and mass spectrometry led to identification of nine C. elegans chondroitin proteoglycan core proteins, none of which have homologs in vertebrates or other invertebrates such as Drosophila or Hydra. CPG-1/CEJ-1 and CPG-2 are expressed during embryonic development and bind chitin, suggesting a structural role in the egg. Simultaneous depletion of CPG-1/CEJ-1 and CPG-2 recapitulated the cytokinesis defect observed in the sqv mutants. Studies are underway to identify the function of these proteoglycans in cell division and whether other arrays of proteoglycans exist in other invertebrates.
Movie M1 (click on picture below to run movie)
Normal cell division in buffer-injected embryos.
Movie M3
cpg-1/cpg-2(RNAi) embryos fail to complete the first cell division.