Microtubule organization and cell geometry

Area of Science:

• Cell Biology
• Biophysics
• Computational Biology

Background:

• Nondividing animal cells typically exhibit radial microtubule organization from a single microtubule organizing center (MTOC).
• Cellular geometry is not always spherical, prompting investigation into its effect on microtubule orientation.

Purpose of the Study:

• To systematically study the influence of elliptical cell geometry on microtubule orientational distribution.
• To model microtubule-cell boundary interactions with increasing complexity.

Main Methods:

• Developed four computational models of increasing complexity for microtubule nucleation and boundary interaction.
• Modeled microtubule (MT) binding with fixed residence time (M0), MT sliding (MS), MT stabilization by polarity factors (MP), and combined sliding and stabilization (MSP).

Main Results:

• The baseline model (M0) showed transverse biaxial order due to boundary interactions along the shorter cell axis.
• MT sliding (MS) reoriented order along the longitudinal axis.
• Polarization mechanisms (MP, MSP) overrode geometric bias, establishing unipolar order along either the short or long cell axis.

Conclusions:

• Cell geometry significantly impacts microtubule organization, initially favoring biaxial order.
• Polarization mechanisms are crucial for establishing specific unipolar microtubule arrangements, overriding geometric constraints.
• A simplified discrete orientation model can qualitatively reproduce complex polarization behaviors.