Evolution of multicellularity by collective integration of spatial information

  1. Enrico Sandro Colizzi  Is a corresponding author
  2. Renske MA Vroomans
  3. Roeland MH Merks
  1. Mathematical Institute, Leiden University; Origins Center, Netherlands
  2. Informatics Institute, University of Amsterdam; Origins Center, Netherlands
  3. Mathematical Institute, Leiden University; Institute of Biology, Leiden University; Origins Center, Netherlands
21 figures, 7 videos, 1 table and 1 additional file

Figures

Model description.

(a) Adhesion between two cells is mediated by receptors and ligands (represented by a bitstring, see Hogeweg, 2000). The receptor of one cell is matched to the ligand of the other cell and vice …

The eco-evolutionary setup of the model.

(a) A population of N=200 cells moves by chemotaxis towards the peak of the gradient, which in this season is located at the left boundary of the grid. (b) At the end of the season, cells divide, the …

A group of cells performs chemotaxis efficiently in a noisy shallow gradient.

(a) Distance of the centre of mass of N=50 cells from the peak of the gradient as a function of time, for different values of γ[-4,6] (five independent runs for each value), together with the average …

Indivdual cell trajectories are noisy, also within a cluster.

(a) The movement of a single cell. (b) Typical movement of a cluster of strongly adhering cells, and of the cells inside the cluster. Cells are placed on the right of the field and move towards …

The evolution of multicellularity.

(a) Multicellularity (γ>0) rapidly evolves in a population of N=200 cells with τs=105. (b) Multicellularity only evolves when seasons are sufficiently long τs50*103; unicellular strategies evolve when seasons are …

Interference competition between adhering and non-adhering cells explains evolutionary bistability.

We let a simulation run for τs=30×103 MCS and then record the distance from the peak of the gradient, for two different populations of cells - one non-adhering (in red, γ=-4) and one adhering (in blue, γ=6), …

Appendix 1—figure 1
Diffusion exponent approximation.

(a) We log-log transformed the data (the shaded area is the relative error Var(MSD(Δt))/MSD(Δt) ). (b) We fitted a polynomial function to the data, then took the derivative of the polynomial function. (c,d) …

Appendix 1—figure 2
The speed of a cluster towards the peak of the gradient saturates with larger cluster sizes.

For each cluster size, we ran five independent simulations. Each dot corresponds to one simulation. Their average (per cluster size) generates the line. All other parameters as in main text.

Appendix 1—figure 3
The flow field of a cluster of cells with and without gradient.

(a) With chemoattractant gradient. (b) Without chemoattractant gradient. In both cases N=50 cells with γ=6 are placed at the centre of the field (All other parameters as in main text).

Appendix 1—figure 4
Chemotaxis of a rigid cluster.

(a) τp=5. (b) μp=0.5. In both cases N=50 cells with γ=6 are placed on the right of the field and move towards higher concentration of the gradient (the semicircle indicates the resource location, where the …

Appendix 1—figure 5
Collective vs. individual chemotaxis for different values of persistence strength μp[0,10].

The plots show the displacement over time of the centre of mass of a single cell (indigo) and that of a cluster of 50 cells (green). Note that the x axis is different in different plots. The value …

Appendix 1—figure 6
Collective vs. individual chemotaxis for different values of chemotactic strength μχ[0.1,5].

The plots show the displacement over time of the centre of mass of a single cell (indigo) and that of a cluster of 50 cells (green). The value of μχ used in main text is indicated by the Default …

Appendix 1—figure 7
Large cells perform chemotaxis more efficiently than clusters of small cells.

Each line corresponds to one simulation with a given combination of number of cells N and cell size AT, and shows the distance of the centre of mass of the cluster of cells from the peak of the …

Appendix 1—figure 8
Simple algorithm for segment extraction.

(a) Visual explanation of the algorithm, with a cartoon representation of a cell track with cell positions recorded at regular time intervals. Images 1-4 represent subsequent stages of the …

Appendix 2—figure 1
Surface tension distribution for a population of cells that evolve adhesion, compared to the distribution of adhesion strength for randomly generated ligands and receptors.

The data for adhering cells are taken from the same simulation used for main text Figure 5a, over 10 seasons after reaching evolutionary steady state with τs=1003 MCS. Black: all vs. all surface tension …

Appendix 2—figure 2
The evolution of multicellularity (and uni-cellularity) for different values of persistent migration strength μp[1,5].

For μp=1, the inset shows the surface tension for τs>200×103 MCS. All other parameters and initialisation are as in main text Figure 5a.

Appendix 2—figure 3
The evolution of multicellularity (and uni-cellularity) for different values of chemotactic strength μχ[0.5,2].

All other parameters and initialisation are as in main text Figure 5a.

Appendix 2—figure 4
The evolution of multicellularity (and uni-cellularity) when resources are spread for a chemoattractant gradient that decreases parallel from resources distributed on the entire side of the lattice.

All other parameters and initialisation are as in main text Figure 5.

Appendix 2—figure 5
The evolution of multicellularity (and uni-cellularity) with a steep, noiseless gradient (kχ=10, pχ=0=0).

All other parameters and initialisation are as in main text Figure 5.

Appendix 3—figure 1
Emergence of collective behaviour and evolution of multicellularity are robust to changing the mechanism of chemotaxis.

(a) The emergence of collective chemotaxis when individual cells cannot sense the gradient; (b) the evolution of multicellularity (and uni-cellularity) under these conditions. μCIL - the strength of …

Appendix 4—figure 1
The evolution of multicellularity (and uni-cellularity) when adhesion is costly.

Different lines correspond to the evolutionary steady state at different season duration τs for different values of costs cm, as indicated in the figure. All other parameters and initialisation are …

Videos

Video 1
Inefficient chemotaxis of a single cell.
Video 2
Chemotaxis of a cluster of adhering cells.

All cells have the same colour to show how the migration of the cluster as a whole resembles that of an amoeba.

Video 3
Inefficient chemotaxis of a cluster of non-adhering cells.
Video 4
The same cluster of adhering cells.

Cell colour indicates the direction of migration, to emphasise the streaming dynamics within the cluster.

Video 5
Video of an evolutionary simulation, starting with neutrally adhering cells (γ=0).

The season changes every 100*103 MCS.

Video 6
Over time a population of non-adhering cells spread throughout the lattice, when seasons are short.

The season changes every 10*103 MCS. For all cells γ=-4. Mutation rate is set to zero to emphasise the spatial population dynamics.

Video 7
Over time a population of adhering cells ends up in the centre of the lattice when seasons are short.

The season changes every 10*103 MCS. For all cells γ=6. Mutation rate is set to zero.

Tables

Table 1
Parameters.
ParameterExplanationValues
L2lattice size500 × 500 lattice sites
TBoltzmann temperature16 AUE
λcell stiffness5.0 AUE/[lattice site]2
ATcell targetarea50 lattice sites
Cell adhesion
Jαminimum J value between cells4 AUE/[lattice site length]
Jαminimum J value between cell and medium8 AUE/[lattice site length]
νlength of receptor and ligand bitstring24 bits
νlength ligand bitstring for medium adhesionsix bits
Cell migration and chemotaxis
μpstrength of persistent migration3.0 AUE
τpduration of persistence vector50 MCS
μχstrength of chemotaxis1.0 AUE
kχscaling factor chemoattractant gradient1.0 molecules/[lattice site length]
pχ=0probability of zero value (’hole’) in gradient0.1 [lattice site]−1
Evolution
Npopulation size200 cells
τsduration of season5 × 103 - 150 × 103 MCS
hddistance from gradient peak where fitness is 1250 [lattice site length]
μR,Ireceptor and ligand mutation probability0.01 per bit, per replication
  1. AUE: Arbitrary Units of Energy (see Hamiltonian in Model Section); lattice site: unit of area; lattice site length: unit of distance; MCS: Monte Carlo Step (unit of time).

Additional files

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