Rong Li - Stowers Institute for Medical Research

I. Regulatory circuits that control cell polarization
The ability of cells to break symmetry and establish a robust polar axis does not rely on any pre-existing external asymmetry. Environmental cues or cues provided from a cell’s history harness this intrinsic ability to establish polarity in physiologically required orientations. We have used yeast as a model organism to explore the intrinsic mechanisms that can drive cell polarization. Our previous work suggested that two different positive feedback loops are capable of driving symmetry breaking, with one involving actin cytoskeleton-dependent transport and the other involving the GTPase cycle of Cdc42. Recently we have used quantitative imaging and mathematical modeling to investigate the general principles that underlie the dynamic maintenance of cell polarity. We are presently extending the quantitative analysis to the entire set of proteins that define the polar cortical domain in order to understand the dynamic organization of various functional modules at the site of polarized growth.

II. Control of actin dynamics during cell polarization and motility
The actin cytoskeleton plays major roles in physiological processes such as cell polarization and cell motility. These functions are intimately related to actin’s dynamic properties. Our work has been focused on the nucleation step of actin filament assembly because this is the rate limiting step in actin polymerization and is an important target for regulation. Through genetic analysis and in vitro actin polymerization assays, we identified several highly conserved protein factors, such as the Arp2/3 complex and a WASP family protein, that are required for assembly of cortical actin filaments. Our current work focuses on understanding the structural basis for the activity of these actin assembly factors using cryo electron microscopy and fluorescence spectroscopy, and the in vivo function and regulation of these proteins using yeast and mouse models.

III. Using fluorescence correlation spectroscopy (FCS) and FLIM-based FRET measurements to understand protein dynamics and interactions in live cells
Achieving a quantitative understanding of cellular systems requires temporally and spatially resolved characterization of dynamic molecular interactions in live cell settings. We have been exploring the use of FCS and fluorescence cross correlation spectroscopy (FCCS) to study cytosolic and nuclear biochemistry of mobile molecules tagged with autofluorescent proteins. We have recently applied this analysis to the MAP kinase signaling cascade and obtained useful parameters for quantitative modeling of this highly conserved signaling cascade. We are also exploring the use of fluorescence lifetime measurement (FLIM)-based FRET analysis to decipher the in vivo protein interactions in compact and complex cytoskeletal structures involved in cell division.

IV. Adaptive evolution of the cell division system
A hallmark of biological systems is their remarkable ability to adapt to external or internal perturbations through rapid generation of heritable phenotypic variations. It has been hypothesized that the evolvability of cellular systems is embedded within the complex design features of the underlying molecular networks, which in turn are built through evolutionary processes. We are using yeast and cultured mammalian cells as models to understand whether and how the cell division system is capable of rapid adaptive evolution, how the evolved pathways are linked to the pre-existing molecular network and how cells generate rapid genomic and transcriptome changes to drive the evolutionary process.

V. The design principles in the mitotic exit control network
Successful cell division is marked not only by the physical separation of progeny cells but more importantly by the correct inheritance of genetic materials. Pioneering work in yeast has shown that mitosis and cytokinesis during cell division are coordinated through an intricate signaling network that controls the exit from mitosis. This network has a great deal of complexity and functional redundancy which underlie the robustness and adaptability that have been observed with this important cell cycle control. We have begun to use computational approaches to study the network design principles of the mitotic exit control. Our goal is to use interweaving modeling and experimentation to understand the timing and spatial sensor functions of this network and to explore the adaptive response of the network when individual components are inhibited.

VI. Asymmetric cell division during mouse oocyte maturation
Mouse oocytes undergo polarization during meiosis II, during which the centrally located spindle moves to a subcortical region where a cortical actin cap that contains myosin-II assembles. This asymmetric placement of the spindle and formation of the actin-based contractile structure are critical for extrusion of the polar body. Our recent work using a reconstituted system showed that the cortical actomyosin structure can be induced by microinjected DNA-coated beads through a pathway of chromatin-directed cortical myosin-II assembly that involves the MAP kinase cascade and the small GTPase Ran. Ongoing experiments are being carried out to elucidate the biochemical details of this unique pathway of regulation of the cortical cytoskeleton.

VII. The cellular basis of autosomal dominant polycystic kidney disease (ADPKD)
Cells that constitute mammalian epithelial and endothelial tissues have the ability to detect and adjust to significant environmental stress while carrying out their specialized functions. Loss of such ability could result in altered cell polarity, morphology and proliferation that ultimately lead to diseases. In polarized renal epithelial cells, the apical surface is marked by a single cilium that is thought to act as a mechanical sensor mediated through cilia-associated proteins such as polycystin 1 and 2. Mutations in these proteins result in autosomal dominant polycystic kidney disease (ADPKD), the most common human genetic disease. We are using a combination of network modeling, mouse genetics, and microaray analysis to understand how loss of polycystin function gives rise to ADPKD.

Academic Appointment: Professor, Department of Molecular & Integrative Physiology, The University of Kansas School of Medicine

Selected Publications

Deng M, Gao J, Suraneni P, Li R. Kinetochore-Independence Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs. PLoS ONE. 2009;4:e5249. Abstract

Li H, Guo F, Rubinstein B, Li R. Actin-driven chromosomal motility leads to symmetry breaking in mammalian meiotic oocytes. Nat Cell Biol. 2008;10:1301-1308. Abstract

Rancati G, Pavelka N, Fleharty B, Noll A, Trimble R, Walton K, Perera A, Staehling-Hampton K, Seidel CW, Li R. Aneuploidy Underlies Rapid Adaptive Evolution of Yeast Cells Deprived(Deng et al., 2009) of a Conserved Cytokinesis Motor. Cell. 2008;135:879-893. Abstract

Li R, Gundersen GG. Beyond polymer polarity: how the cytoskeleton builds a polarized cell. Nat Rev Mol Cell Biol. 2008;9:860-873. Abstract

Slaughter BD, Huff JM, Wiegraebe W, Schwartz JW, Li R. SAM domain-based protein oligomerization observed by live-cell fluorescence fluctuation spectroscopy. PLoS ONE. 2008;3:e1931. Abstract

Rouiller I, Xu XP, Amann KJ, Egile C, Nickell S, Nicastro D, Li R, Pollard TD, Volkmann N, Hanein D. The structural basis of actin filament branching by the Arp2/3 complex. J Cell Biol. 2008;180:887-895. Abstract

Li X, Magenheimer BS, Xia S, Johnson T, Wallace DP, Calvet JP, Li R. A tumor necrosis factor-alpha-mediated pathway promoting autosomal dominant polycystic kidney disease. Nat Med. 2008;14:863-868. Abstract

Wedlich-Soldner R, Li R. Yeast and fungal morphogenesis from an evolutionary perspective. Semin Cell Dev Biol. 2008;19:224-233. Abstract

Li R. Cytokinesis in development and disease: variations on a common theme. Cell Mol Life Sci. 2007;64:3044-58. Abstract

Rancati G, Li R. Polarized cell growth: double grip by CDK1. Curr Biol. 2007;17:R600-603. Abstract

Slaughter BD, Schwartz JW, Li R. Mapping dynamic protein interactions in MAP kinase signaling using live-cell fluorescence fluctuation spectroscopy and imaging. Proc Natl Acad Sci U S A. 2007;104:20320-20325. Abstract

Marco E, Wedlich-Soldner R, Li R, Altschuler SJ, Wu LF. Endocytosis Optimizes the Dynamic Localization of Membrane Proteins that Regulate Cortical Polarity. Cell. 2007;129:411-422. Abstract

Deng M, Suraneni P, Schultz RM, Li R. The Ran GTPase Mediates Chromatin Signaling to Control Cortical Polarity during Polar Body Extrusion in Mouse Oocytes. Dev Cell. 2007;12:301-308. Abstract

Lister IM, Tolliday NJ, Li R. Characterization of the minimum domain required for targeting budding yeast myosin II to the site of cell division. BMC Biol. 2006;4:19. Abstract

Yoo Y, Wu X, Egile C, Li R, Guan JL. Interaction of N-WASP with hnRNPK and its role in filopodia formation and cell spreading. J Biol Chem. 2006;281:15352-15360. Abstract

Slaughter B, Li R. Toward a molecular interpretation of the surface stress theory for yeast morphogenesis. Curr Opin Cell Biol. 2006;18:47-53. Abstract

Egile C, Rouiller I, Xu XP, Volkmann N, Li R, Hanein D. Mechanism of Filament Nucleation and Branch Stability Revealed by the Structure of the Arp2/3 Complex at Actin Branch Junctions. PLoS Biol. 2005;3:e383. Abstract

Brandman O, Ferrell JE, Jr., Li R, Meyer T. Interlinked fast and slow positive feedback loops drive reliable cell decisions. Science. 2005;310:496-498. Abstract

Bosl WJ, Li R. Mitotic-exit control as an evolved complex system. Cell. 2005;121:325-333 Abstract

Verplank L, Li R. Cell Cycle Regulated Trafficking of Chs2 Controls Actomyosin Ring Stability during Cytokinesis. Mol Biol Cell. 2005;16:2529-2543. Abstract

Li R. Neuronal Polarity: Until GSK-3 Do Us Part. Curr Biol. 2005;15:R198-200. Abstract

Kowalski JR, Egile C, Gil S, Snapper SB, Li R, Thomas SM. Cortactin regulates cell migration through activation of N-WASP. J Cell Sci. 2005;118:79-87. Abstract

Pan F, Egile C, Lipkin T, Li R. ARPC1/Arc40 mediates the interaction of the actin-related protein 2 and 3 complex with Wiskott-Aldrich syndrome protein family activators. J Biol Chem. 2004;279:54629-54636. Abstract

Wedlich-Soldner R, Li R. Closing the loops: new insights into the role and regulation of actin during cell polarization. Exp Cell Res. 2004;301:8-15. Abstract

Li R, Wai SC. Bacterial cell polarity: a "swarmer-stalked" tale of actin. Trends Cell Biol. 2004;14:532-536. Abstract

Smith LG, Li R. Actin polymerization: riding the wave. Curr Biol. 2004;14:R109-111. Abstract

Frank M, Egile C, Dyachok J, Djakovic S, Nolasco M, Li R, Smith LG. Activation of Arp2/3 complex-dependent actin polymerization by plant proteins distantly related to Scar/WAVE. Proc Natl Acad Sci U S A. 2004;101:16379-16384. Abstract

Jonsdottir GA, Li R. Dynamics of yeast Myosin I: evidence for a possible role in scission of endocytic vesicles. Curr Biol. 2004;14:1604-1609. Abstract

Wedlich-Soldner R, Wai SC, Schmidt T, Li R. Robust cell polarity is a dynamic state established by coupling transport and GTPase signaling. J Cell Biol. 2004;166:889-900. Abstract

Gouin E, Egile C, Dehoux P, Villiers V, Adams J, Gertler F, Li R, Cossart P. The RickA protein of Rickettsia conorii activates the Arp2/3 complex. Nature. 2004;427:457-461. Abstract

Wedlich-Soldner R, Li R. Spontaneous cell polarization: undermining determinism. Nat Cell Biol. 2003;5:267-270. Abstract

Paw BH, Davidson AJ, Zhou Y, Li R, Pratt SJ, Lee C, Trede NS, Brownlie A, Donovan A, Liao EC, Ziai JM, Drejer AH, Guo W, Kim CH, Gwynn B, Peters LL, Chernova MN, Alper SL, Zapata A, Wickramasinghe SN, Lee MJ, Lux SE, Fritz A, Postlethwait JH, Zon LI. Cell-specific mitotic defect and dyserythropoiesis associated with erythroid band 3 deficiency. Nat Genet. 2003;34:59-64. Abstract

Kreishman-Deitrick M, Egile C, Hoyt DW, Ford JJ, Li R, Rosen MK. NMR analysis of methyl groups at 100-500 kDa: model systems and Arp2/3 complex. Biochemistry (Mosc). 2003;42:8579-8586. Abstract

Yarrow JC, Lechler T, Li R, Mitchison TJ. Rapid de-localization of actin leading edge components with BDM treatment. BMC Cell Biol. 2003;4:5. Abstract

Wedlich-Soldner R, Altschuler S, Wu L, Li R. Spontaneous cell polarization through actomyosin-based delivery of the Cdc42 GTPase. Science. 2003;299:1231-1235. Abstract

Tolliday N, Pitcher M, Li R. Direct evidence for a critical role of myosin II in budding yeast cytokinesis and the evolvability of new cytokinetic mechanisms in the absence of myosin II. Mol Biol Cell. 2003;14:798-809. Abstract

Tolliday N, VerPlank L, Li R. Rho1 directs formin-mediated actin ring assembly during budding yeast cytokinesis. Curr Biol. 2002;12:1864-1870. Abstract

Soulard A, Lechler T, Spiridonov V, Shevchenko A, Li R, Winsor B. Saccharomyces cerevisiae Bzz1p is implicated with type I myosins in actin patch polarization and is able to recruit actin-polymerizing machinery in vitro. Mol Cell Biol. 2002;22:7889-7906. Abstract

Tolliday N, Bouquin N, Li R. Assembly and regulation of the cytokinetic apparatus in budding yeast. Curr Opin Microbiol. 2001;4:690-695. Abstract

Lechler T, Jonsdottir GA, Klee SK, Pellman D, Li R. A two-tiered mechanism by which Cdc42 controls the localization and activation of an Arp2/3-activating motor complex in yeast. J Cell Biol. 2001;155:261-270. Abstract

Volkmann N, Amann KJ, Stoilova-McPhie S, Egile C, Winter DC, Hazelwood L, Heuser JE, Li R, Pollard TD, Hanein D. Structure of Arp2/3 complex in its activated state and in actin filament branch junctions. Science. 2001;293:2456-2459. Abstract

Lippincott J, Shannon KB, Shou W, Deshaies RJ, Li R. The Tem1 small GTPase controls actomyosin and septin dynamics during cytokinesis. J Cell Sci. 2001;114:1379-1386. Abstract

Uruno T, Liu J, Zhang P, Fan Y, Egile C, Li R, Mueller SC, Zhan X. Activation of Arp2/3 complex-mediated actin polymerization by cortactin. Nat Cell Biol. 2001;3:259-266. Abstract

Li R. Mitosis: shutting the door behind when you leave. Curr Biol. 2000;10:R781-784. Abstract

Lippincott J, Li R. Nuclear envelope fission is linked to cytokinesis in budding yeast. Exp Cell Res. 2000;260:277-283. Abstract

Lechler T, Shevchenko A, Li R. Direct involvement of yeast type I myosins in Cdc42-dependent actin polymerization. J Cell Biol. 2000;148:363-373. Abstract

Shannon KB, Li R. A myosin light chain mediates the localization of the budding yeast IQGAP-like protein during contractile ring formation. Curr Biol. 2000;10:727-730. Abstract

Egile C, Loisel TP, Laurent V, Li R, Pantaloni D, Sansonetti PJ, Carlier MF. Activation of the CDC42 effector N-WASP by the Shigella flexneri IcsA protein promotes actin nucleation by Arp2/3 complex and bacterial actin-based motility. J Cell Biol. 1999;146:1319-1332. Abstract

Field C, Li R, Oegema K. Cytokinesis in eukaryotes: a mechanistic comparison. Curr Opin Cell Biol. 1999;11:68-80. Abstract

Winter DC, Choe EY, Li R. Genetic dissection of the budding yeast Arp2/3 complex: a comparison of the in vivo and structural roles of individual subunits. Proc Natl Acad Sci U S A. 1999;96:7288-7293. Abstract

Winter D, Lechler T, Li R. Activation of the yeast Arp2/3 complex by Bee1p, a WASP-family protein. Curr Biol. 1999;9:501-504. Abstract

Li R. Bifurcation of the mitotic checkpoint pathway in budding yeast. Proc Natl Acad Sci U S A. 1999;96:4989-4994. Abstract

Shannon KB, Li R. The multiple roles of Cyk1p in the assembly and function of the actomyosin ring in budding yeast. Mol Biol Cell. 1999;10:283-296. Abstract

Lippincott J, Li R. Dual function of Cyk2, a cdc15/PSTPIP family protein, in regulating actomyosin ring dynamics and septin distribution. J Cell Biol. 1998;143:1947-1960. Abstract

Lippincott J, Li R. Sequential assembly of myosin II, an IQGAP-like protein, and filamentous actin to a ring structure involved in budding yeast cytokinesis. J Cell Biol. 1998;140:355-366. Abstract

Lechler T, Li R. In vitro reconstitution of cortical actin assembly sites in budding yeast. J Cell Biol. 1997;138:95-103. Abstract

Winter D, Podtelejnikov AV, Mann M, Li R. The complex containing actin-related proteins Arp2 and Arp3 is required for the motility and integrity of yeast actin patches. Curr Biol. 1997;7:519-529. Abstract

Li R. Bee1, a yeast protein with homology to Wiscott-Aldrich syndrome protein, is critical for the assembly of cortical actin cytoskeleton. J Cell Biol. 1997;136:649-658. Abstract

Winter D, Podtelejnikov AV, Mann M, Li R. The complex containing actin-related proteins Arp2 and Arp3 is required for the motility and integrity of yeast actin patches. Curr Biol. 1997;7:519-529. Abstract

Deng M, Gao J, Suraneni P, Li R. Kinetochore-Independence Chromosome Poleward Movement during Anaphase of Meiosis II in Mouse Eggs. PLoS ONE. 2009;4:e5249.