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Letter

Nature Cell Biology 9, 193–200 (1 February 2007) | doi:10.1038/ncb1536

Chemotaxis in shallow gradients is mediated independently of PtdIns 3-kinase by biased choices between random protrusions

Natalie Andrew & Robert H Insall

Current models of eukaryotic chemotaxis propose that directional sensing causes localized generation of new pseudopods. However, quantitative analysis of pseudopod generation suggests a fundamentally different mechanism for chemotaxis in shallow gradients: first, pseudopods in multiple cell types are usually generated when existing ones bifurcate and are rarely made de novo; second, in Dictyostelium cells in shallow chemoattractant gradients, pseudopods are made at the same rate whether cells are moving up or down gradients.