Research / Clinical Summary

Arshad Desai, PhD Associate Professor, Cellular & Molecular Medicine Cancer Genes and Genome Program Contact by Email

Eukaryotic chromosome segregation requires kinetochores, organelles that assemble on condensing chromosomes to form dynamic attachment sites for spindle microtubules. Errors in kinetochore function contribute to chromosomal instability during tumorigenesis and potentially also to birth defects.

Because of their specific roles in cell division, kinetochore components are attractive targets for anti-mitotic chemotherapy. Molecular analysis of kinetochores in metazoans has been limited by their essential nature, rarity of their constituents, and difficulties in translating mechanochemical functions into biochemical assays.

Two central unanswered questions are: (1) how is the localized region of the chromosome where the kinetochore assembles specified? and (2) how is the initiation of kinetochore assembly translated into the formation of an interface that interacts with spindle microtubules to direct chromatid segregation?

We are addressing these questions using functional analysis in the nematode C. elegans, and extending some of the studies to human cells. Our work capitalizes on the unique access provided by the one-cell stage C. elegans embryo for analyzing the function of essential gene products. Using a combination of RNA interference-based genomics and biochemistry, we are rapidly generating a comprehensive component list for the mitotic chromosome segregation machinery.

In addition, we have developed powerful imaging-based assays to place newly identified as well as known proteins into specific functional groups and to define their site of action within the substructure of the kinetochore. Kinetochore specification is intimately associated with CENP-A, a centromere-specific histone H3 variant. In one project, we are defining the mechanism of CENP-A deposition following fertilization in C. elegans, focusing on proteins implicated by unbiased genomics as playing key roles in this essential process.

A second project is focused on understanding how initiation of kinetochore assembly is propagated to form the interface with spindle microtubules. We have discovered widely conserved new proteins that play a central role at the interface between kinetochores and spindle microtubules and are extending analysis of these proteins to both an in vitro level and to human cells. Dissecting the mechanisms driving physical segregation of the genome during cell division should shed light on the origins of aneuploidy in cancer cells and provide new potential targets for anti-mitotic chemotherapy.