This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.106.098038v1 93/4/1124    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Prost, J. Articles by Joanny, J.-F. Search for Related Content PubMed PubMed Citation Articles by Prost, J. Articles by Joanny, J.-F.

Dynamical Control of the Shape and Size of Stereocilia and Microvilli

Physico Chimie Curie, Institut Curie, Paris, France

Correspondence: Address reprint requests to J. Prost, Tel.: 33-40-79-45-00; E-mail: jacques.prost{at}curie.fr.

We discuss theoretically the shape of actin-based protrusions such as stereocilia or microvilli that have important functions in many biological systems. These linear protrusions are dynamical structures continuously renewed by treadmilling: actin polymerizes at the tip of the cilium and depolymerizes in its bulk. They also often have a well-controlled length such as in the hair bundles of the inner ear cells where they appear in a graded staircase structure. Recent experimental results by another group of researchers show that the treadmilling velocity of the hair cell stereocilia is proportional to their length. We use generic arguments to describe the physics of stereocilia taking into account the effect of many individual proteins at a coarse-grained level by a few phenomenological parameters. At the tip of the cilium, we find that actin polymerization induces an effective pressure. Below the tip, the shape of the cilium is determined by depolymerization: Agreement with the observed shape requires that depolymerization occurs at least in two steps. Under these conditions, we calculate the cilium shape and provide physical grounds for the proportionality between treadmilling velocity and cilium length. We also calculate the penetration of the stereocilium in the actin cortical layer.

This article has been cited by other articles:

				Y. Lan and G. A. Papoian The Stochastic Dynamics of Filopodial Growth Biophys. J., May 15, 2008; 94(10): 3839 - 3852. [Abstract] [Full Text] [PDF]

				G. Lefevre, V. Michel, D. Weil, L. Lepelletier, E. Bizard, U. Wolfrum, J.-P. Hardelin, and C. Petit A core cochlear phenotype in USH1 mouse mutants implicates fibrous links of the hair bundle in its cohesion, orientation and differential growth Development, April 15, 2008; 135(8): 1427 - 1437. [Abstract] [Full Text] [PDF]