Xavier Darzacq

Xavier Darzacq

Assistant Professor of Genetics, Genomics and Development
Dept of Molecular & Cell Biology
(510) 664-4853
Research Expertise and Interest
Transcription regulation during cellular differentiation. Linking the biophysical rules of nuclear organization and gene expression control mechanism.
Research Description

Our group studies transcription focusing on the role imposed by nuclear architecture on the molecules regulating it. We use a model system of cellular differentiation of human primary dermal fibroblasts into myofibroblasts, which is relevant to wound healing. Among the specificities of this system, we show that the maintenance of the fibroblast state depends on a specialized non-canonical mediator complex, which is becoming one of the central projects of the group. Moreover several transcription factors equally expressed in the two states are required for the differentiation process and we will focus our research on the regulation of their activity as transcriptional regulators.

Over the last five years we developed new techniques to study the organization of proteins in the nucleoplasm with resolutions in the range of a few nanometers as well as procedures to track single molecules in live cells in order to measure their specific and unspecific interactions with chromatin as well as their space exploration properties. Together with more established techniques such as fluorescent in situ hybridization (FISH), live cell visualization of nucleic acids (Lac, Tet and MS2) or photobleaching techniques (FRAP, FLIP), we can image transcription regulation with the appropriate temporal resolution (a few milliseconds to a few days) and at single molecule resolution within live cells.

Our recent findings suggest a very strong link in between the organization of the nucleoplasm and the biophysical rules governing macromolecular assemblies. While a decade ago the fast mobility of proteins in the nucleoplasm lead to diffusion models, we are now envisioning models where proteins are guided on DNA or protein networks controlling their exploration properties (diffusion can be guided). We are currently deeply involved in providing evidences for such a model by characterizing the nucleoplasmic distribution of chromatin and non-chromatin components of the nucleus as well as measurements of single molecules explorations and binding.

Within the next decade, great technological advances are expected in the field of microscopy, fluorophore chemistry as well as cellular engineering with new genome editing techniques already in place. These new developments will put us in an ideal situation to monitor several different molecules simultaneously  (therefore defining molecular multicomponent complexes) with resolutions close to that of electron microscopy. It will be a unique opportunity to integrate the cellular and biochemical know how of an institute strong of a long experience in gene regulation with advances in biophysics, chemistry and imaging in order to reveal the rules governing transcription regulation within a living cell and eventually living organisms.

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