Spontaneous center formation in Dictyostelium discoideum

Abstract

Dictyostelium discoideum (D.d.) is a widely studied amoeba due to its capabilities of development, survival, and self-organization. During aggregation it produces and relays a chemical signal (cAMP) which shows spirals and target centers. Nevertheless, the natural emergence of these structures is still not well understood. We present a mechanism for creation of centers and target waves of cAMP in D.d . by adding cell inhomogeneity to a well known reaction-diffusion model of cAMP waves and we characterize its properties. We show how stable activity centers appear spontaneously in areas of higher cell density with the oscillation frequency of these centers depending on their density. The cAMP waves have the characteristic dispersion relation of trigger waves and a velocity which increases with cell density. Chemotactically competent cells react to these waves and create aggregation streams even with very simple movement rules. Finally we argue in favor of the existence of bounded phosphodiesterase to maintain the wave properties once small cell clusters appear.

Simulation modeling of cAMP induced Dictyostelium aggregation by using object-oriented Pharo programming language

“…Then the active centers of aggregation appeared. Till now, this phenomenon is enigmatic, but probably, as it was mentioned above, is related to the cell inhomogeneity [3]. For modeling this process we used the finding of lattice "gems", described earlier for cultured human fibroblasts in the real (nonvirtual) experiment [8].…”

“…As a result, a huge bulk of information on this phenomenon was obtained during past decades [2]. Special attention is paid to one of the central points of self-organization: emergence of the active centers of aggregation and cell inhomogeneity [3].…”

Experimental observation of boundary-driven oscillations in a reaction–diffusion–advection system

“…The Martiel-Goldbeter model 20 is a reaction-diffusion model proposed in 1987 to describe pattern formation in D. discoideum and has been successfully used to describe spiral formation, 3,21 wave advection, 22 spontaneous center formation, 23 and cell streaming. 24 Changing the parameters in the model allows us to describe the system at different points during the starvation process or with knocked-out genes.…”

Social Conflicts in <em>Dictyostelium discoideum</em> : A Matter of Scales

“…Stochastic choices are thought to be involved at the onset of aggregation, in establishing aggregation centers (Gregor et al, 2010); during aggregation, in the decisions whether to follow the cAMP gradient (Rossine et al, 2020); and even during development, in mixing of pre-spore and pre-stalk cells within a slug (Weijer, 1999). On the other hand, phenotypic heterogeneity in isogenic populations can also result from deterministic sources, such as the distribution of cell cycle phase in asynchronously dividing cultures (Jang & Gomer, 2011;Gruenheit et al, 2018) or the spatial distribution of cell density (Vidal-Henriquez & Gholami, 2019).…”