Random walk and cell morphology dynamics inNaegleria gruberi

Abstract

AbstractAmoeboid cell movement and migration are wide-spread across various cell types and species. Microscopy-based analysis of the model systemsDictyosteliumand neutrophils over the years have uncovered generality in their overall cell movement pattern. Under no directional cues, the centroid movement can be quantitatively characterized by their persistence to move in a straight line and the frequency of re-orientation. Mathematically, the cells essentially behave as a persistent random walker with memory of two characteristic time-scale. Such quantitative characterization is important from a cellular-level ethology point of view as it has direct connotation to their exploratory and foraging strategies. Interestingly, outside the amoebozoa and metazoa, there are largely uncharacterized species in the excavate taxon Heterolobosea including amoeboflagellateNaegleria. While classical works have shown that these cells indeed show typical amoeboid locomotion on an attached surface, their quantitative features are so far unexplored. Here, we analyzed the cell movement ofNaegleria gruberiby employing long-time phase contrast imaging to automatically track individual cells. We show that the cells move as a persistent random walker with two time-scales that are close to those known inDictyosteliumand neutrophils. Similarities were also found in the shape dynamics which is characterized by the appearance, splitting and annihilation of the curvature waves along the cell edge. Our analysis based on the Fourier descriptor and a neural network classifier point to importance of morphology features unique toNaegleriaincluding complex protrusions and the transient bipolar dumbbell morphologies.