Cell Movements and Mechanical Force Distribution During the Migration of Dictyostelium Slugs

Abstract

Abstract. Migration of Dictyostelium discoideum slugs results from coordinated movement of their constituent cells. It is generally assumed that each cell contributes to the total motive force of the slug. However, the basic mechanisms by which mechanical forces (traction and resistive forces) are transmitted to the substrate, their magnitude and their location, are largely unknown. In this work, we performed detailed observations of cell movements by fluorescence microscopy using twodimensional (2D) slugs. We show that 2D slugs share most of the properties of 3D ones. In particular, waves of movement propagate in long 2D slugs, and slug speed correlates with slug length as found in 3D slugs. We also present the first measurements of the distribution of forces exerted by 2D and 3D slugs using the elastic substrate method. Traction forces are mainly exerted in the central region of the slug. The large perpendicular forces around slug boundary and the existence of parallel resistive forces in the tip and/or the tail suggest an important role of the sheath in the transmission of forces to the substrate.

Migration of Dictyostelium slugs: Anterior‐like cells may provide the motive force for the prespore zone

“…Dictyostelium slugs are able to develop on very soft polyacrylamide substrata and migrate at the same speed as on agar [Rieu et al, 2004]. They induce large displacements of fluorescent beads (i.e., about 5 lm) when using a substratum of Young's modulus E 5 5.5 kPa (see Figs.…”

“…Siegert and Weijer [Siegert and Weijer, 1992] proposed that the prestalk cell movement is organized by a rotating scroll wave of cAMP, which serves as pacemaker for the formation of planar cAMP waves, which in turn direct periodic forward movement of prespore cells. Periodic motions and optical waves with the same period have been observed in slugs of many Dictyostelium strains [Dormann and Weijer, 2001] and in twodimensional Dictyostelium slugs [Rieu et al, 2004].…”

“…The mechanisms by which motive force is transmitted to the substratum and their location have been the subject of numerous speculations and hypotheses. Recently, we were able to directly measure traction force using elastic substrata [Rieu et al, 2004[Rieu et al, , 2005. We clearly identified traction forces mostly in the prespore region balanced by friction forces in the tip and in the tail of the slug.…”

“…Slugs move at a constant speed proportional to slug length [Rieu et al, 2004]. There is a characteristic pattern of movements in slugs: cells in the anterior prestalk zone show vigorous lateral movement which is often helical around the central core of the aerial portion of the tip [Siegert and Weijer, 1992], while cells in the central prespore zone move straight forward in the direction of slug migration in a generally periodic fashion [Breen and Williams, 1994;Dormann et al, 1996].…”

An elasto-visco-plastic model of cell aggregates

“…Cell aggregates or multicellular systems appear in embryo development [29,28,26,39,24] or in blood flow, but they are also involved in other processes such as hydra aggregates motion, dictyostelium slugs crawling [34,33] and they are of considerable interest in tumour growth [1,2,14,15,42]. Their mechanical behavior is often assimilated to soft biological tissues, usually corresponding to viscoelastic materials or to non-Newtonian fluids [17].…”