Integrated Calendar

Firing-rate (FR) or neural-mass models are widely used for studying computations performed by neural populations. Despite their success, classical firing-rate models do not capture spike timing effects on the microscopic level such as spike synchronization and are difficult to link to spiking data in experimental recordings. For large neuronal populations, the gap between the spiking neuron dynamics on the microscopic level and coarse-grained FR models on the population level can be bridged by mean-field theory formally valid for infinitely many neurons. It remains however challenging to extend the resulting mean-field models to finite-size populations with biologically realistic neuron numbers per cell type (mesoscopic scale). In this talk, I present a mathematical framework for mesoscopic populations of generalized integrate-and-fire neuron models that accounts for fluctuations caused by the finite number of neurons. To this end, I will introduce the refractory density method for quasi-renewal processes and show how this method can be generalized to finite-size populations. To demonstrate the flexibility of this approach, I will show how synaptic short-term plasticity can be incorporated in the mesoscopic mean-field framework. On the other hand, the framework permits a systematic reduction to low-dimensional FR equations using the eigenfunction method. Our modeling framework enables a re-examination of classical FR models in computational neuroscience under biophysically more realistic conditions.

Calcium signaling serves as a means of regulation of virtually all processes in a cell throughout the life of an organism, from fertilization to death. One of the multiple aspects of calcium signaling is store-operated calcium entry (SOCE) that has been raising a great interest in the last 30 years. Disregarded first for its allegedly negligible effect on calcium changes inside a cell, it is being reconsidered nowadays as a ubiquitous phenomenon regulating pivotal processes, such as transcription, immune response and others. As other pathways of calcium signaling, SOCE is regulated by multiple proteins, required for adjusting calcium levels to current cellular needs. Among them is SARAF, a protein that has been shown to negatively regulate SOCE, thus preventing calcium excess inside a cell. I will try to elaborate on my attempts to decipher the mysterious mechanism of its regulation.

One of the key advantages in using light-sensitive hydrogel biomaterials is the ability to spatially structure cell scaffolds with three-dimensional mechanical cues that guide cellular morphogenesis. However, this has proven difficult because of the high toxicity associated with the cross-linking interactions. To overcome this challenge, we developed a new paradigm in micro-patterning using a reversible temperature-induced phase transition from liquid to solid vis-à-vis lower critical solubility temperature (LCST). This facilitates reduced transport kinetics of the polymer chains in solution, thus enabling crosslinking that is truly compatible with cell-laden 3D culture. Cellularized constructs were patterned to reveal a difference in morphogenesis between chemically crosslinked “stiffer” and physically crosslinked “softer” regions. Emphasizing the importance of mechanical heterogeneity in cellular morphogenesis, the results validate cutting-edge technology that can provide scientists with a robust set of tools for engineering cell and tissue growth in three dimensions.

Exocrine glands in our bodies secret copious amounts of cargo (like- sweat, saliva, digestive enzymes, chemokines, etc.) via. giant secretory vesicles, that are micron-scale in diameter. During the secretion of these giant vesicles, a large amount of the membrane is constantly added to the apical surface of the cells that can perturb its size, composition, and function that are vital to cell survival. Hemostatic maintenance of the cell surface in terms of size, shape, and composition is extremely challenging in the face of continuous secretion, which what we ventured to understand. We use a combination live-cell imaging and correlative light and electron microscopy (CLEM) approach, to uncover a novel a mechanism of exocytosis allowing the secretory cells to maintain membrane homeostasis during secretion. I will present to you data to describe what we call as - the crumpling and sequestration model of exocytosis.

TBA