MMPB Subgroup Contributed Talks

Jonathan Miller

University of Dundee

"Modelling firing characteristics of T6SS"

In this talk I will develop a mathematical model of of the Type VI bacterial secretion system. The Type VI Secretion System (T6SS) is a transmembrane macro-molecular contractile machine able to dynamically and repeatedly compete against both prokaryotes and eukaryotes. Whilst many of the core molecular components of the T6SS have been identified, there are open questions regarding how the T6SS is regulated in response to stimuli. Here I develop a stochastic differential equation model that describes post-translational regulation of the T6SS. The model is solved numerically and used to explore how the time between successive firing events allows for spatial reorientation of firing and thus for a bacterium to respond to spatially localised external stimuli.

Divyoj Singh

Indian Institute of Science

"Continuum model for Planar cell polarity"

Planar Cell Polarity (PCP) is an evolutionary conserved phenomenon in which cells in an epithelium are polarized within the plane of the tissue. Disruptions in PCP can often lead to developmental abnormalities such as defects in neural tube formation and atypical organ shape. The emergent multi-scale dynamics of PCP has been investigated experimentally and computationally through focusing on different modules (set of molecular players) revealing asymmetric protein localisation on cell boundaries as the primary PCP mechanism. Additional ingredient in the PCP establishment is the global cue in the form of tissue-wide protein concentrations. Despite multiple mechanistic modelling attempts, an analytic understanding of the system has not yet been comprehensively achieved. Here, we present a minimal continuum model, derived from the microscopic interactions of the proteins, to study the emergence of macroscopic tissue-wide polarity. We obtain necessary and sufficient conditions and diverse parameter regimes for different cases of establishing PCP and its disruptions. We also solve the model numerically to study the model where analytic solution is not possible. Finally, we compare the model results to other existing mechanistic approaches to draw conceptual parallels between them, with the goal of identifying design principles of PCP.

Ushasi Roy

Indian Institute of Science Bangalore, India

"Does intermediate intercellular adhesion leads to faster migration of a multicellular cluster?"

Diverse biological processes like embryogenesis, morphogenesis, neurogenesis, regeneration, wound healing, and disease propagation like cancer-metastasis involve numerous cells exhibiting coherent migration. Multicellular clusters undergo dynamic rearrangement while relocating — bigger clusters split, smaller sub-clusters collide and reassemble, gaps continually appear and disappear, and cells (and the clusters as a whole) undergo variations in shape and orientation. The connections between cell-level adhesion and cluster-level dynamics, as well as the resulting consequences for cluster properties such as migration velocity, remain poorly understood. To unveil the underlying mechanics of collective migration of two-dimensional cell clusters concertedly tracking chemical gradients, we develop a generic computational framework based on the cellular Potts model which captures cell shape changes and cluster rearrangement. We find that cells have an optimal adhesion strength that maximizes cluster migration speed. The optimum negotiates a tradeoff between preserving cell-cell contact and maintaining configurational freedom, and we identify maximal variability in the cluster aspect ratio as a revealing signature. Our results suggest a collective benefit for intermediate cell-cell adhesion.U. Roy and A. Mugler. Phys. Rev. E 103, 032410 (2021).

Tsuyoshi Mizuguchi

Osaka Prefecture University

"Inhomogeneity of Japanese name distribution"

The size distributions of persons' names, i.e., how many people share a certain name, obeys Zipf's law in various countries or areas. There is, however, a regionality for each country or area, and the ingredients of the distributions differ from each other. We statistically analyze the distributions of persons' family and given names obtained from a telephone directory to characterize their heterogeneities. By using Kullback–Leibler divergence, the inhomogeneity of name distribution are analyzed both from the viewpoint of person and prefecture.