For a living cell to function properly, its cellular processes must be strictly controlled not only in time but also in space. We are interested in how intracellular spatial organization on the micron-length scale is achieved by nanometer-sized proteins. We investigate this problem in the context of the microtubule cytoskeleton.

In eukaryotes, a wide range of cellular processes such as cell division, cell migration, axonal growth and assembly of flagella and cilia rely on the dynamic and precise organization of microtubules into specialized architectures. Increasingly sophisticated genomic and proteomic analyses have now provided us with a near-complete 'parts-list' of the proteins involved in assembling these microtubule-based structures. However, the molecular mechanisms underlying the proper formation and activity of even the minimal functional units of these structures still remain poorly understood. We aim to bridge this knowledge gap by reconstituting minimal units of microtubule-based architectures in vitro from the individual components. We use a diverse set of experimental tools in our endeavor: integrating angstrom and nanometer-length scale information from X-ray crystallography and single-molecule visualization techniques with micron-length scale analysis of microtubule architectures using multi-color TIRF microscopy-based in vitro assays and cellular analyses of the cytoskeletal structures.

Currently, our research is focused on microtubule organization during cell division. Specifically, we are interested in the molecular mechanisms underlying the assembly of the spindle midzone, an interdigitating array of microtubules, which emerges between segregating chromosomes at anaphase. In current models, the midzone play a key role in specifying the site of cell division by keeping the segregated chromosomes apart and promoting the ingression of the cell cleavage furrow. However, we still do not understand how even the basic features of this structure such as shape and size are determined. This is largely because midzone assembly is a complex process involving a number of mechanical (e.g. motor proteins) and regulatory components (e.g. kinases), many of which have multiple functions during mitosis. To overcome this challenge, we take a reductionist approach and build minimal units of this cell division apparatus from purified proteins to address how the collective activity of midzone proteins contributes to its proper assembly and function. We are also using this approach to dissect the molecular mechanisms underlying microtubule organization in other cellular contexts.