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Forming, Confining, and Observing Microtubule-Based Active Nematics
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Recent experiments challenge active nematics classification. This study shows cell accumulation at topological defects is driven by antisymmetric active forces, unifying contractile and extensile nematics.

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Area of Science:

  • Physics, Biophysics
  • Cell Biology
  • Materials Science

Background:

  • Active nematics are typically classified as contractile or extensile.
  • Neural progenitor cells with topological defects challenge this binary classification.
  • Understanding cell behavior in active nematics is crucial for developmental biology and tissue engineering.

Purpose of the Study:

  • To investigate the behavior of cells within active nematics, particularly around topological defects.
  • To reconcile experimental observations of cell accumulation at +1 defects with existing theories.
  • To propose a unified framework for understanding active nematic behavior.

Main Methods:

  • Particle-level modeling of cellular active nematics.
  • Development and analysis of a derived continuum theory.
  • Qualitative comparison of model predictions with experimental data on neural progenitor cells.

Main Results:

  • Both particle-level models and continuum theory reproduce cell accumulation at +1 topological defects.
  • Cellular accumulation is attributed to two previously overlooked antisymmetric active forces.
  • The findings apply to all types of +1 defects, irrespective of nematic classification.

Conclusions:

  • Antisymmetric active forces are key drivers of cell behavior in active nematics.
  • This work provides a unified explanation for cell accumulation at topological defects.
  • The findings have implications for understanding cellular active nematics in various biological and engineered systems.