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toca-1 is in a novel pathway that functions in parallel with a SUN-KASH nuclear envelope bridge to move nuclei in

Yu-Tai Chang1, Daniel Dranow, Jonathan Kuhn

  • 1Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.

Genetics
|November 15, 2012
PubMed

Insights

Researchers identified a new pathway for nuclear migration in C. elegans, distinct from known SUN-KASH protein bridges. This novel, likely actin-dependent, mechanism involves the TOCA-1 protein, revealing new insights into cell and developmental processes.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Genetics

Background:

  • Nuclear positioning is crucial for fundamental cellular and developmental processes like migration, differentiation, and polarity.
  • SUN and KASH proteins form bridges across the nuclear envelope, mediating many nuclear positioning events.
  • Other nuclear migration pathways exist but are poorly understood.

Purpose of the Study:

  • To identify and characterize novel mechanisms of nuclear migration.
  • To find new genes and pathways involved in nuclear positioning.
  • To understand how nuclei move independently of SUN-KASH bridges.

Main Methods:

  • Conducted a nonbiased forward genetic screen in Caenorhabditis elegans.
  • Utilized a temperature-sensitive mutation in the unc-84 gene (encoding a SUN protein) to enhance screening sensitivity.
  • Isolated mutations that specifically disrupted nuclear migration only in the unc-84 mutant background.

Main Results:

  • Identified eight 'emu' (enhancer of the nuclear migration defect of unc-84) mutations.
  • One mutation (yc20) was found in the toca-1 gene.
  • TOCA-1 mediates P-cell nuclear migration in a cell-autonomous manner.
  • TOCA-1 is conserved in humans and involved in actin organization during endocytosis.

Conclusions:

  • Discovered a novel, likely actin-dependent, pathway for nuclear migration.
  • This pathway functions in parallel to the established SUN-KASH protein bridges.
  • TOCA-1 is a key player in this previously unknown nuclear migration mechanism.
  • Other identified 'emu' mutations may represent additional components of this novel pathway.

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