Fig 1.
The mechanical model of actin, α-actinin and myosin minifilaments in MEDYAN.
Double helix structure of actin filament is represented as a series of cylinders (red) connected together at hinges (black spheres). Stretching (Uistr), bending (Uibend) and cylinder-cylinder excluded volume (Uijvol) interactions are elaborated. Crosslinkers (green) and myosin MF (blue) experience stretching potentials (Uiα and UiMF respectively). More details are provided in the Methods section and the Supporting Methods (section 2 in S1 Text).
Fig 2.
Representative snapshots show network morphologies from simulations of unipolar bundles under different crosslinker and myosin mole ratios with respect to the actin concentration.
Each panel shows a steady state network configuration of actin (colored in red) along with bound myosin minifilaments (blue) and α–actinin (green). Mole ratios of myosin and α-actinin with respect to actin are held at values mentioned along abscissa and ordinate of the grid respectively.
Fig 3.
Representative snapshots show network morphologies from simulations of apolar bundles under different crosslinker and myosin mole ratios with respect to the actin concentration.
Each panel shows a steady state network configuration of actin (colored in red) along with bound myosin minifilaments (blue) and α–actinin (green). Mole ratios of myosin and α-actinin with respect to actin are held at values mentioned along abscissa and ordinate of the grid respectively.
Fig 4.
Dendrograms illustrating clustering of different resultant actin network morphologies from either unipolar (left) or apolar (right) bundle initial configurations.
Distributions of distances between minus-minus, minus-plus and plus-minus ends were used to construct dissimilarity matrices for both unipolar and apolar cases. Agglomerative cluster trees were encoded from the above-mentioned dissimilarity matrices and then drawn as dendrograms. The three largest clusters are shown in red, blue and green along with representative final snapshots. α:A values are indicated close to the snapshots while M:A values are indicated for each sub-cluster. Clades corresponding to bundle-like configurations are colored in green while aster-like configurations are colored in blue. Intermediate states that do not resemble either network morphologies are colored in red.
Fig 5.
Schematic of preferred network morphologies under different values of triad.
Cartoon illustration of dominant network morphologies of bundles expected in a) unipolar and b) apolar initial configurations at different ranges of treadmilling factor namely χ = 0, 0>χ≤1.0 (0.1, 0.3, 0.6, 1.0) and χ>1.0 (3.0, 6.0, 10.0) Morphologies observed at discrete values of triad along with results from clustering (S5 Fig in S1 Text) were used to propose the map above. Colored voxels are used to represent distinct zones of preferred network morphologies expected. Dotted line represents uncertainty in the boundary. Dotted lines within white bands represent the crosslinker- and myosin-dependent boundaries between stable and unstable networks.
Fig 6.
The effects of treadmilling factor (χ) and myosin sliding on the morphologies of BAInit networks are illustrated.
Upper panel shows a cartoon of filaments (red) with barbed ends (black tips) representing various orientational arrangements that were realized in our simulations, determined by the interplay between the treadmilling rate and myosin activity. a-c) Representative final snapshots from simulations at M:A 0.0225 at various crosslinker mole ratio (α:A) at χ values 0.1 (a), 0.3 (b) and 1.0 (c) are shown. d) For networks with χ = 1.0, probability of finding NMIIA (dotted line) and α-actinin (solid line) along bundle axis are plotted.