Cell shape and orientation control galvanotactic accuracy

TL;DR

This paper models how cell shape and orientation influence galvanotactic accuracy, revealing complex effects of cell geometry on electric field sensing and proposing mechanisms for cell elongation in response to sensor redistribution.

Contribution

It extends previous models by incorporating cell shape and orientation, analyzing their impact on galvanotaxis accuracy and sensor-based field estimation.

Findings

Cells have more information about the field when aligned with it.

Sensor averaging can bias cells towards the short axis.

Cell elongation may depend on sensor migration direction.

Abstract

Galvanotaxis is believed to be driven by the redistribution of transmembrane proteins and other molecules, referred to as "sensors", through electrophoresis and electroosmosis. Here, we update our previous model of the limits of galvanotaxis due to stochasticity of sensor movements to account for cell shape and orientation. Computing the Fisher information, we find that cells in principle possess more information about the electric field direction when their long axis is parallel to the field, but that for weak fields maximum-likelihood estimators of the field direction may actually have lower variability when the cell's long axis is perpendicular to the field. In an alternate possibility, we find that if cells instead estimate the field direction by taking the average of all the sensor locations as its directional cue ("vector sum"), this introduces a bias towards the short axis, an effect not present for isotropic cells. We also explore the possibility that cell elongation arises downstream of sensor redistribution. We argue that if sensors migrate to the cell's rear, the cell will expand perpendicular the field - as is more commonly observed - but if sensors migrate to the front, the cell will elongate parallel to the field.