Modelling of Dictyostelium Discoideum Movement in Linear Gradient of Chemoattractant

TL;DR

This study develops a position-dependent advection-diffusion model to describe and analyze the chemotactic movement of Dictyostelium discoideum in linear cAMP gradients, revealing time-dependent changes in movement coefficients and nonlinear displacement behavior.

Contribution

The paper introduces a quantitative model fitting experimental trajectories, capturing the nonlinear and time-dependent features of amoeba chemotaxis in cAMP gradients.

Findings

Diffusion and drift coefficients decrease over time.

Cells exhibit nonlinear variance in movement.

Nonlinear terms dominate large-scale displacement.

Abstract

Chemotaxis is a ubiquitous biological phenomenon in which cells detect a spatial gradient of chemoattractant, and then move towards the source. Here we present a position-dependent advection-diffusion model that quantitatively describes the statistical features of the chemotactic motion of the social amoeba {\it Dictyostelium discoideum} in a linear gradient of cAMP (cyclic adenosine monophosphate). We fit the model to experimental trajectories that are recorded in a microfluidic setup with stationary cAMP gradients and extract the diffusion and drift coefficients in the gradient direction. Our analysis shows that for the majority of gradients, both coefficients decrease in time and become negative as the cells crawl up the gradient. The extracted model parameters also show that besides the expected drift in the direction of chemoattractant gradient, we observe a nonlinear dependency of the corresponding variance in time, which can be explained by the model. Furthermore, the results of the model show that the non-linear term in the mean squared displacement of the cell trajectories can dominate the linear term on large time scales.