Polarity sorting of axonal microtubules: a computational study

Area of Science:

• Cell Biology
• Neuroscience
• Computational Biology

Background:

• Microtubule (MT) organization is crucial for neuronal development and function.
• Axonal MTs exhibit a predominant plus-end-out polarity, but the underlying mechanisms remain incompletely understood.

Purpose of the Study:

• To computationally model and test the "polarity sorting" hypothesis for axonal MT organization.
• To investigate the roles of motor proteins and cross-linkers in MT transport dynamics.

Main Methods:

• Development of a computational model simulating motor-based axonal transport of short MTs.
• Inclusion of immobilized cytoplasmic dynein, plus-end-directed motors, and static cross-linker proteins in the simulations.

Main Results:

• Dynein-based transport alone can explain the predominant plus-end-out MT polarity.
• Transient motor attachments and static cross-linkers are necessary to replicate observed MT pauses and reversals.
• Static cross-linkers create "tug-of-war" dynamics, explaining MT immobility.

Conclusions:

• The polarity sorting model, incorporating dynein motors and cross-linkers, successfully explains axonal MT organization.
• Predictions include disrupted MT transport upon static cross-linker inhibition and altered polarity sorting upon dynein inhibition.