The number of cells crossing a boundary is a weak indicator of chemotaxis

Authors

• AC Szatmary
• R Nossal

Abstract

Chemotaxis, the motion of cells directed by a gradient of chemoattractant molecules, is difficult to measure. Chemotaxis is frequently inferred based on how many cells cross a boundary in a chemotaxis assay, for example how many cells crawl into the filter in the filter migration assay or how many cells crawl into a defined region in the under agarose assay or agarose spot assay. The major limitation of this approach is that motion is not necessarily directed by the chemoattractant gradient. To determine how reliably methods based on boundary crossing can indicate chemotactic motion of cells, we used information about the gradient sensitivity of neutrophils and MDA-MB-231 breast cancer cells to model how much gradient sensing increases the rate of boundary crossing in these assays relative to a random-motility control, and over what duration. As part of this effort, we determined the chemoattractant profile in the filter migration assay for filters of low porosity. Our results show that neutrophils can sense chemoattractant gradients generated in the under agarose and agarose spot assays for 1–2 h. In the filter assay, a neutrophil would be able to reliably perceive a gradient for about 10 h., while an MDA-MB-231 cell would have a much smaller, but still measurable chemotactic response. Chemotaxis of MDA-MB-231 cells, and cells with similar gradient sensitivity, cannot be measured by counting the cells in the agarose spot and under agarose assays; moreover, measurement of chemotaxis of these cells using the filter assay requires robust controls.

Scientific Focus Area: Cell Biology

This page was last updated on Friday, March 26, 2021