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CGEF-1 and CHIN-1 regulate CDC-42 activity during asymmetric division in the Caenorhabditis elegans embryo.

The anterior-posterior axis of the Caenorhabditis elegans embryo is elaborated at the one-cell stage by the polarization of the partitioning (PAR) proteins at the cell cortex. Polarization is established under the control of the Rho GTPase RHO-1 and is maintained by the Rho GTPase CDC-42. To understand more clearly the role of the Rho family GTPases in polarization and division of the early embryo, we constructed a fluorescent biosensor to determine the localization of CDC-42 activity in the living embryo. A genetic screen using this biosensor identified one positive (putative guanine nucleotide exchange factor [GEF]) and one negative (putative GTPase activating protein [GAP]) regulator of CDC-42 activity: CGEF-1 and CHIN-1. CGEF-1 was required for robust activation, whereas CHIN-1 restricted the spatial extent of CDC-42 activity. Genetic studies placed CHIN-1 in a novel regulatory loop, parallel to loop described previously, that maintains cortical PAR polarity. We found that polarized distributions of the nonmuscle myosin NMY-2 at the cell cortex are independently produced by the actions of RHO-1, and its effector kinase LET-502, during establishment phase and CDC-42, and its effector kinase MRCK-1, during maintenance phase. CHIN-1 restricted NMY-2 recruitment to the anterior during maintenance phase, consistent with its role in polarizing CDC-42 activity during this phase.

Pubmed ID: 19923324


  • Kumfer KT
  • Cook SJ
  • Squirrell JM
  • Eliceiri KW
  • Peel N
  • O'Connell KF
  • White JG


Molecular biology of the cell

Publication Data

January 15, 2010

Associated Grants

  • Agency: NIGMS NIH HHS, Id: 5 T32 GM-08349
  • Agency: NIGMS NIH HHS, Id: GM-052454

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Caenorhabditis elegans
  • Caenorhabditis elegans Proteins
  • Cell Division
  • Cell Polarity
  • Embryo, Nonmammalian
  • GTPase-Activating Proteins
  • Green Fluorescent Proteins
  • Guanine Nucleotide Exchange Factors
  • Models, Biological
  • Molecular Sequence Data
  • Mutation
  • Myosin Type II
  • Protein Binding
  • Protein Transport
  • Signal Transduction
  • cdc42 GTP-Binding Protein
  • rho GTP-Binding Proteins