Chemical biology of cell division

The ability to accurately segregate genetic material into daughter cells is essential for the survival of an organism. Errors in this process can result in developmental defects and diseases in humans. We take a multidisciplinary approach to determine the molecular and physical basis for how, during cell division, exactly one copy of our genome is delivered to each daughter cell.

Our research can be divided into three areas:

1. Observing cell division

Cell division involves the transport of chromosomes along tracks of tubulin polymers. Motor proteins drive this transport, and the direction and distance of movement is regulated by networks of signaling proteins. We use state-of –the-art microscopy methods to track at the highest resolution possible the dynamics of the cargo, the tracks, the motor proteins, and key regulators in single dividing cells. Live cell imaging methods include multi-mode real-time confocal, differential interference contrast (DIC), fluorescence recovery after photobleaching (FRAP), fluorescence resonance energy transfer (FRET), photoactivation of fluorescence and fluorescent speckle microscopy (FSM). These analyses have allowed measurements of transport dynamics that provide necessary input to build quantitative models for cell division.

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2. Reconstituting cell division processes with purified components

A measure of our understanding of the biological processes we observe is our ability to reconstitute them in vitro. During cell division the organization of the microtubule tracks into a bipolar spindle shape involves the transport of microtubules relative to each other. This can be directly observed in vertebrate mitotic spindles. We have reconstituted this cell division process using pure recombinant Eg5 (kinesin-5), a widely conserved mitotic kinesin, and microtubules. This assay system represents a first step towards an in vitro ‘minimal spindle’ that we are using to test key models for the assembly and function of the mitotic spindle.

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3. Perturbing cell division to examine mechanisms

Central to our approach in addressing long-standing questions relating to cell division is the use of cell-permeable small organic molecules that allow us to intervene in cellular processes on a time-scale of minutes to seconds. This temporal control over protein function is particularly suited to the study of cell division, a process that takes minutes, with several steps occurring within seconds. The reversibility of a small molecule’s effect also provides opportunities to examine how the cellular system recovers from either the inhibition or activation of its components. By combining the use of small molecule probes with state-of-the-art microscopy to examine the dynamics of cell division we match, as closely as possible, the time-scale of observations to that of the perturbation. To apply this approach, we have developed methods for the discovery, chemical synthesis and characterization of bio-active small molecules and assays that exploit the control over protein function offered by small molecules. The processes we have examined using this approach include: (1) how chromosomes attach to microtubules during mitosis, (2) bipolar spindle assembly, (3) regulation of chromosome-microtubule attachment, (4) cell division checkpoint signaling.

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Laboratory of Chemistry and Cell Biology, Rockefeller University
Flexner Hall Rm 359C, 1230 York Ave, NY 10021