Main research interests of our laboratory are focused on the understanding of the spatiotemporal dynamics of the actin cytoskeleton aand calcium in health and disease.
Main research interests
Historically, advances in understanding the mechanisms underlying key events of actin organisation been driven by innovations in microscopy that provide greater spatial and temporal resolution coupled to appropriate immunochemical, genetic, and biochemical tools. Until recently, the state-of-the-art microscopy has not been informative about real-time spatiotemporal dynamics of the actin cytoskeleton. Little is also known about the mechanisms generating actin structures in mechanobiology.
Two fundamentally different mechanisms exist to generate actin networks: self-assembly and self-organisation. Self-assembly involves the physical association of motor proteins to actin, for instance, to assemble actin filaments into equilibrium networks. Self-organised actin networks are at steady state kept far from equilibrium by the constant input of energy. They arise solely through the local physical interactions of actin filaments initiated by a spontaneous instability such as symmetry breaking events, for example, when actin-polymerisation dynamics or intrinsic mechanical stress of actin networks spontaneously change. Conclusive understanding of these rearrangements involves the tight coupling between biochemical and physical properties of three components of the actin cytoskeleton: (i) actin kinetics: actin protomer association/dissociation into filamentous actin (F-actin); (ii) actin dynamics: the assembly of filaments into actin structures; and (iii) mechanics: the cytoskeleton generates, senses, and transmits mechanical forces.
Main objectives of our laboratory are focused on the application and development of novel ultra-sensitive, live-cell fluorescence microscopy techniques with a spatial resolution down to the nanoscale (super-resolution microscopy), superior to conventional optical microscopes, to investigate these processes. A list of ongoing and future projects is summarised below:
Mechanical forces in immunology
Cellular interactions are often ruled by physical changes due to motion, so-called mechanical force. Such forces are involved during molecular rearrangements and most obviously when cells form close contacts, avoid each other, or reshape to change morphology. Thus, forces play an important role in many biomedical processes; particularly during spreading of cancerous cells and cell-cell contact of immune cells (for instance during the formation of the immunological synapse during an immune response). Consequently, medical research increasingly recognises the important link between forces and molecular re-organization within biological systems. However, how cells dynamically adjust their microscopic structure to control their mechanical properties remains elusive. In order to find new ways of detecting disease-related malfunctions or of manipulating processes relating to forces, it is essential to be able to measure the microscopic changes leading to mechanical force generation.
Actin cytoskeletal dynamics shape T-cell activation
These changes are ultimately driven by the actin cortex, the most important substructure of the cytoskeleton. The cell cortex is a thin network of actin, and associated proteins that underlies the plasma membrane. It enables cells to resist and transmit extracellular stresses, perform mechanical work, and change shape. Cortical structural and mechanical properties depend strongly on its relative turnover rates of its constituents caused by continuous molecular reorganisation of the actin network and its filament length-distribution, but quantitative data on these dynamics remain elusive. This research project aims to combine a variety of experimental techniques with molecular computer simulations to analyse how molecular binding dynamics of actin filaments set the coarse grained protein turnover and consequently the mechanical properties of the cellular actin cortex in living cells.
Calcium signalling in T-cell triggering
As a second messenger, calcium plays a vital role in relaying information from cell-surface receptors into changes in cellular mechanisms, including cytoskeletal rearrangement. In T cells, calcium signalling is a key aspect in its development, survival, and activation. Given the transient, dynamic nature of calcium, a high temporal resolution is crucial in measuring calcium levels over time. And, while such studies have been done, they are typically done with only a few cells at a time. Because calcium responses can be heterogeneous between , it is imperative to measure many cells at once while still depicting individual calcium levels. CalQuo2 is recently updated user-friendly, MATLAB based software that can robustly analyses calcium patterns of individual cells within hundreds to thousands of cells that have been captured using fluorescence microscopy.