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Physics of multicellular systems
The development of animals, starting from a single cell to produce a fully formed organism, is a fascinating process. Its study is currently advancing at a rapid pace thanks to combined experimental and theoretical progress, yet many fundamental questions remain to be answered.
This course will address the fundamental theoretical concepts underlying the self-organization of multicellular systems, from gene regulation to the mechanics of active biological materials. The course will be based on various concepts from theoretical physics: dynamical systems, soft and active matter, the mechanics of continuous media, numerical modeling, etc.
Advances in sequencing, genetic manipulation, microscopy, and ex vivo culture are bringing an unprecedented amount of detailed and quantitative information on the individual and collective cell behaviors that underlie the development and function of multicellular systems.
This is accompanied by new developments in the theory and modeling of these dynamical processes, building on physical concepts from diverse fields, such as statistical mechanics (particularly of out-of equilibrium systems such as active matter), soft matter, dynamical systems, pattern formation, information theory, and mechanics.
In addition to the understanding of animal development, it is anticipated that advances in the study of multicellular systems will be essential for applications such as the production of organs ex vivo and the rational design of therapies for complex diseases.
The lectures will present an introduction to this burgeoning field of research at the broad interface of physics and biology. They will be accompanied by practical sessions (TDs) with both theoretical and numerical components.
Syllabus
- Gene regulatory networks and their dynamics
- Patterning I (morphogen gradients, positional information)
- Patterning II (self-organization, Turing models)
- Interacting cells, lateral inhibition, dynamical systems approaches
- From cell to tissue tension (cortical tension, measurement methods, tension inference, tissue tension: origin and limits of the concept)
- Vertex models of tissues models (2D vertex models of epithelia, topological rearrangements, rigidity transitions and jamming)
- Continuous models of tissues - dissipation and nematic order (Onsager variational principle, active polar fluid)
- Continuous models of tissues - tissue growth (population dynamics, growth of a spheroid, homeostatic pressure)
- Final project
Prerequisites
No prerequisite in physics but general knowledge in statistical physics, dynamical systems and continuous mechanics will help.
Basic mathematic tools are essential (integration by parts, linear algebra, partial differential equations...) and Python programming skills will be required for the TDs.
Evaluation
Study and presentation of a scientific article with the reproduction of some of its results numerically.
The project starts three weeks before the exam.
Oral presentation by groups of 2-3 students.