Abstract: 

Cells package their genomic DNA into a complex with proteins called chromatin. Chromatin is partitioned into subcompartments that differ from each other with respect to their compaction, molecular composition and biological function. One example are the micron-sized spherical heterochromatin foci that are present in several differentiated cell types and that are readily visible under the microscope. It is a key question how such compartments can form even though diffusion constantly mixes the nuclear interior. One biophysical mechanism that can explain this phenomenon is liquid-liquid phase separation, which creates biomolecular condensates via multivalent interactions. Another one is polymer-polymer phase separation, which changes the folding of chromosomes via bridging interactions among chromatin loci. I will briefly describe the differences between these phase separation mechanisms and will present recent experiments that assess the dynamic properties of DNA-based condensates formed in the test tube and heterochromatin foci in living cells. I will compare these experiments to the different models and briefly discuss the implication for the dynamic regulation of chromatin subcompartments.

Bio:

A physicist and molecular biologist, Fabian obtained his PhD in Physics at the German Cancer Research Center (DKFZ) in 2012. Following his doctorate, he held two post-doctoral positions at the DKFZ and at Columbia University. Since 2019, Fabian is a group leader at the Center for Integrative Biology (CBI) in Toulouse. His research interests lie in the biophysical properties of chromatin and the molecular mechanisms underlying epigenetic regulation. Fabian's research team uses methods of molecular biophysics and synthetic biology to build artificial systems for studying and manipulating the spread and transfer of epigenetic modifications. Using these systems, they seek to understand how histone modifications are faithfully deposited and maintained. Fabian is a recipient of the Otto Haxel Award (2009) and the Nikon Young Investigator Award (2013) in recognition of his work.