@phdthesis{12964,
  abstract     = {Pattern formation is of great importance for its contribution across different biological behaviours. During developmental processes for example, patterns of chemical gradients are
established to determine cell fate and complex tissue patterns emerge to define structures such
as limbs and vascular networks. Patterns are also seen in collectively migrating groups, for
instance traveling waves of density emerging in moving animal flocks as well as collectively migrating cells and tissues. To what extent these biological patterns arise spontaneously through
the local interaction of individual constituents or are dictated by higher level instructions is
still an open question however there is evidence for the involvement of both types of process.
Where patterns arise spontaneously there is a long standing interest in how far the interplay
of mechanics, e.g. force generation and deformation, and chemistry, e.g. gene regulation
and signaling, contributes to the behaviour. This is because many systems are able to both
chemically regulate mechanical force production and chemically sense mechanical deformation,
forming mechano-chemical feedback loops which can potentially become unstable towards
spatio and/or temporal patterning.
We work with experimental collaborators to investigate the possibility that this type of
interaction drives pattern formation in biological systems at different scales. We focus first on
tissue-level ERK-density waves observed during the wound healing response across different
systems where many previous studies have proposed that patterns depend on polarized cell
migration and arise from a mechanical flocking-like mechanism. By combining theory with
mechanical and optogenetic perturbation experiments on in vitro monolayers we instead find
evidence for mechanochemical pattern formation involving only scalar bilateral feedbacks
between ERK signaling and cell contraction. We perform further modeling and experiment
to study how this instability couples with polar cell migration in order to produce a robust
and efficient wound healing response. In a following chapter we implement ERK-density
coupling and cell migration in a 2D active vertex model to investigate the interaction of
ERK-density patterning with different tissue rheologies and find that the spatio-temporal
dynamics are able to both locally and globally fluidize a tissue across the solid-fluid glass
transition. In a last chapter we move towards lower spatial scales in the context of subcellular
patterning of the cell cytoskeleton where we investigate the transition between phases of
spatially homogeneous temporal oscillations and chaotic spatio-temporal patterning in the
dynamics of myosin and ROCK activities (a motor component of the actomyosin cytoskeleton
and its activator). Experimental evidence supports an intrinsic chemical oscillator which we
encode in a reaction model and couple to a contractile active gel description of the cell cortex.
The model exhibits phases of chemical oscillations and contractile spatial patterning which
reproduce many features of the dynamics seen in Drosophila oocyte epithelia in vivo. However,
additional pharmacological perturbations to inhibit myosin contractility leaves the role of
contractile instability unclear. We discuss alternative hypotheses and investigate the possibility
of reaction-diffusion instability.},
  author       = {Boocock, Daniel R},
  isbn         = {978-3-99078-032-9},
  issn         = {2663-337X},
  pages        = {146},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{Mechanochemical pattern formation across biological scales}},
  doi          = {10.15479/at:ista:12964},
  year         = {2023},
}