Gaudenz Danuser

LAB OVERVIEW

The Danuser lab studies how mechanical and chemical signals integrate in the regulation of cytoskeleton dynamics that mediate cell migration and chromosome segregation during cell division. We develop quantitative live cell microscopy and signal processing algorithms to reconstruct the molecular events (activation of signals, assembly, disassembly, and transport of cytoskeletal structures) associated with these processes. Recently, we have expanded our research program with a collaborative project that focuses on the relationship between cytoskeletal plasticity and endocytosis.

2006 HIGHLIGHT

Grouping of kinetochore proteins by their effect on kinetochore microtubule dynamics
Khuloud Jaqaman, Ph.D.
Kinetochores consist of 70 – 100 different proteins that mediate chromosome-microtubule (MT) attachment during mitosis. Little is known about the organization of these proteins in pathways that convert mechanical and/or chemical inputs into regulated MT dynamics required for accurate chromosome alignment and segregation. To address this question we tracked the lengths of single S. cerevisiae kinetochore MTs (kMTs) over time in more than 800 live cell time lapses. We employed a stochastic time series analysis framework, called autoregressive moving average (ARMA) models, to analyze kMT dynamics and compare them between wildtype and strains carrying kinetochore protein mutations. ARMA models extract the dependence of the length of a kMT on its history and on a random number series which embodies the stochastic nature of kMT dynamic instability. This reveals the transitions between kMT states over time, providing us with the means to probe kMT dynamics and their regulation with unprecedented sensitivity. ARMA descriptors also allowed us to define proximity measures for clustering kinetochore proteins based on their effect on the kMT dynamics.
We found that kMT dynamics in the mutants okp1-5 and kip3? are different from those in wildtype, proving that kinetochore proteins do indeed regulate kMT dynamics. We also found that the mutant dam1-1 exhibits three different phenotypes, indicating the central role of Dam1p in maintaining the attachments of kMTs and regulating their dynamics. Furthermore, kMT dynamics resulting from the mutants ipl1-321, kip3? and one phenotype of dam1-1 were equivalent and significantly different from wildtype dynamics, suggesting that Ipl1p, Dam1p and Kip3p form one functional group. Indeed Ipl1p is a kinase upstream of both Dam1p and Kip3p. To our knowledge this is the first time that sufficient data from live cell readouts are available to identify pathways by the effect of gene products on the dynamics of a specific molecular machine. This is a major breakthrough for studies of multi-protein complexes too large for biochemical and structural analyses.

2006 PUBLICATIONS

1. Jaqaman K., Dorn J.F., Jelson, G., Tytell J.D., Sorger, P.K., Danuser G. Comparative Time Series Analysis of Stochastic Molecular Processes: Application to Kinetochore Microtubule Dynamics in Yeast. Biophys. J. 91: 2312-2325. 2006.
2. Cameron L., Yang G., Cimini D., Canman J.C., Kisurina-Evgenieva O., Khodjakov A., Danuser G., and Salmon E.D.S. Kinesin-5 independent poleward flux of kinetochore microtubules in Ptk1 cells. J. Cell Biol. 173:17 – 179. Cover Story.
3. Machacek M. and Danuser G. Morphodynamic profiling of protrusion phenotypes. Biophys. J. 90: 1439 – 1452. 2006.
4. Jaqaman K. and Danuser G. Linking data to models: data regression. Nature Rev. Mol. Cell Biol. 7:813 – 819. 2006.
5. Danuser G. and Waterman-Storer C.M. Quantitative Fluorescent Speckle Microscopy of Cytoskeleton Dynamics. Ann. Rev. Biophys. Biomol. Struct. 35: 361-387. 2006.
6. Meijering E., Smal I., and Danuser G. Tracking in Molecular Bioimaging. IEEE Signal Processing Magazine Special Issue on Molecular and Cellular Bioimaging. 46 – 53. May 2006.

TSRI > Research > Cell Biology