Director, Princeton Bioengineering Initiative
June K. Wu ’92 Professor in Engineering
Professor of Chemical and Biological Engineering
301 Hoyt Laboratory
Ph.D., Harvard University, 2007
B.S., Carnegie Mellon University, 2001
Honors and Awards
- MacArthur Fellow, 2018
- Sloan Research Fellowship, 2014
- NSF CAREER Award, 2013
- NIH New Innovator Award, 2012
- Searle Scholar Award, 2012
- Helen Hay Whitney Fellow, 2008-2010
- Associated Faculty, Department of Molecular Biology
- Associated Faculty, Lewis-Sigler Institute for Integrative Genomics
The Brangwynne lab is focused on elucidating the fundamental principles underlying biological organization, with a particular interest in membrane-less organelles/condensates which form within living cells. Despite having no enclosing membrane, these structures localize biomolecules, including both RNA and protein, into distinct subcellular micro-compartments; examples include processing bodies, neuronal granules and germ (P) granules in the cytoplasm, and Cajal bodies, nucleoli, and PML bodies in the nucleus. We use experimental approaches together with close theory/computation collaborators to study the role of intracellular phase transitions in the assembly of these structures, and the impact of this phase behavior on the flow of genetic information (for a recent review on intracellular phase separation, see Shin & Brangwynne Science 2017). Our work combines the tools and techniques of soft matter physics and engineering with cutting edge cell and molecular biology methods, including advanced light microscope imaging and analysis. We are also heavily invested in the development of technologies for probing endogenous organelles, as well as engineering entirely new kinds of intracellular organelles for biomedical applications.
The Liquid Nucleome
Of the dozens of liquid phase membrane-less bodies in the cell, nuclear bodies are particularly interesting, since they directly interact with and regulate the genome (Fig. 1). Our work to date has focused on nucleoli, the most prominent nuclear body associated with the biogenesis of ribosomes, the protein translation machinery (see e.g. Weber Curr Biol 2015, Berry PNAS 2015, Feric Cell 2016). We are also interested in nuclear bodies associated with the active transcription and processing of other genes, which are associated with condensates such as transcriptional hubs, Cajal bodies, and nuclear speckles. The molecular players underlying phase separation of these structures typically include intrinsically disordered proteins/regions (IDPs/IDRs), and their oligomerization, as well as interactions with RNA. Moreover, DNA is not only restructured in response to RNA/protein-driven phase separation, but itself may phase separate to give rise to higher order genome architecture. The interplay of these effects, and the impacts on biological function, are still largely unclear, and represents a major uncharted universe of non-covalent epigenetic regulation and dynamics. We have various collaborators involved in this work, many of whom are associated with the NIH 4D Nucleome Consortium.
Pathological Protein Aggregation
The liquid phase nature of intracellular condensates has implications not only for physiological function, but also for its dysregulation in disease. Neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimers, and Huntington's disease are associated with solid-like protein inclusions comprised of semi-crystalline amyloid fibers. Interestingly, many of the key IDR/LCS proteins found in RNP bodies are also implicated in these pathologies. Moreover, even in healthy cells, RNP bodies do not always appear to be pure liquids, and often exhibit partially solid-like features. In a review in 2012, we suggested that RNP bodies may represent metastable liquid phases, which can transition into more solid-like forms that could underlie the onset of various protein aggregation pathologies (Weber Cell 2012). Work from our own and other groups has recently provided strong evidence in support of this concept, showing that many liquid phase droplets are indeed metastable. For example, after sitting on a coverslip for several hours, droplets of the fungal protein Whi3 begin to nucleate fibers (Zhang Mol Cell 2015), while droplets of the nucleolar protein FIB1 become progressively more gel-like over time, consistent with time-dependent viscoelastic properties in vivo (Feric Cell 2016).
Membrane-less condensates can play roles within the cell comparable to those described for conventional membrane-bound organelles, including molecular sequestration, facilitating metabolic reactions, and channeling and amplifying intracellular signaling. The name organelle, comes from the fact that these structures are to the cell what our organs are to our bodies. And just as the field of tissue engineering has developed around the potential for organ replacements (i.e. heart, liver, kidney etc.), we are pioneering efforts to develop synthetic organelles for biomedical applications (i.e. organelle diseases) and for various biotechnology applications. This includes efforts to develop actuatable synthetic organelles in human cells, and in synthetic organelles in yeast being pursued in collaboration with the lab of Jose Avalos (Princeton Chemical and Biological Engineering).
Our work on intracellular organization spans biology, engineering, and physics, and we believe that thes efforts have the potential to uncover entirely new physics. For example, although our work has revealed that the thermodynamic concept of liquid-liquid phase equilibrium is useful for understanding the cytoplasm/nucleoplasm, living cells are out-of-equilibrium systems. One primary manifestations of this nonequilibrium behavior is the ATP hydrolysis which occurs throughout the cell, associated with activity of a plethora of ATP-dependent enzymes (molecular motors, helicase etc.) – see e.g. Brangwynne JCB 2008, Brangwynne et.al. PNAS 2011, Feric et.al. Cell 2016. A second related manifestation of intracellular nonequilibrium is post-translational protein modifications (PTMs), such as phosphorylation of particular IDR residues, which tune the intermolecular interactions underlying phase behavior (for a review, see Brangwynne et.al. Nature Physics 2015). Thus, the phase diagrams that we have been able to map in living cells (e.g. Bracha et.al. Cell 2018) may ultimately reflect and underlying non-equilibrium state. How this nonequilibrium behavior impacts classical features of phase behavior, such as nucleation and growth, spinodal decomposition, and criticality, and its dependence on IDR sequence, remain poorly understood and of great interest to us. Some of this work is being pursued together with our theory/computation collaborators, including Mikko Haataja (Princeton Mechanical Engineering), Ned Wingreen (Princeton Molecular Biology), Rohit Pappu (WUSTL), and Thanos Panagiatopoulos (Princeton Chemical and Biological Engineering).
- Shin Y, Brangwynne CP. Liquid phase condensation in cell physiology and disease. Science 357(6357)eaaf4382, 2017
- Shin Y. , Chang Y-C, Lee D.S.W., Berry J., Sanders D.W., Ronceray P., Wingreen N.S., Haataja M.P., Brangwynne CP. Liquid nuclear condensates mechanically sense and restructure the genome. Cell, 2018
- Elbaum-Garfinkle S, Kim Y, Szczepaniak C, Eckmann C, Myong S, Brangwynne CP. The disordered P granule protein LAF-1 drives phase separation into droplets with tunable viscosity and dynamics. Proceedings of the National Academy of Sciences USA, 112(23):7189-7194, 2015
- Feric M, Vaidya N, Harmon TS, Mitrea DM, Zhu L, Richardson TM, Kriwacki RW, Pappu RV, Brangwynne CP. Coexisting liquid phases underlie nucleolar sub-compartments. Cell, 165(7):1686-1697, 2016
- Brangwynne CP, Eckmann CR, Courson DS, Rybarska A, Hoege C, Gharakhani J, Jülicher F, Hyman AA. Germline P granules are liquid droplets that localize by controlled dissolution/condensation. Science, 324: 1729-1732, 2009