Chad Pearson - Research Associate

Cancer onset is associated with changes in cellular protein expression and function, including proteins integral to mitosis. While it is not clear if these changes are causal effects leading to uncontrolled cell growth, it is clear that chromosome loss can lead to cellular transformation. A mechanism for chromosome loss is the amplification of centrosomes. Centrosomes form the two spindle poles organizing microtubules for bipolar mitotic spindle formation. Errors in centrosome duplication can generate multipolar spindles which, during mitosis, multipolar spindles result in unequal chromosome segregation or aneuploidy. Furthermore, multiple centrosomes are found in an exceptional number of transformed cell lines, suggesting that deregulated duplication may lead to uncontrolled cellular growth. Specific cases of tumorigenesis argue that centrosome amplification precedes changes in ploidy. The process of centrosome duplication is not well understood and is limited by the lack of experimental systems for centriole study. Centrioles function as the core organelle which directs centrosome duplication and nucleation of microtubules. Basal bodies, for the formation of cilia and flagella, are analogous structures to centrioles. In addition to cancer, molecular defects in basal body and centriole components have been linked with the pleiotropic Bardet-Biedl Syndrome (BBS). Tetrahymena is a ciliated eukaryote with established techniques for genetic modification; characteristics that enable cytological studies and isolation of basal body protein for in vitro biochemical studies. The objective of my work is to utilize Tetrahymena basal bodies to study molecular mechanisms for basal body duplication. I have identified several novel basal body proteins and am developing high resolution cytological assays to study the duplication process. The specific aims of my work are: (1) to define TtBbs5 localization and function at basal bodies, (2) to identify novel basal body proteins, and (3) to characterize basal body duplication in vivo. Using a combination of techniques I plan to detail a molecular view of the basal body and centriole duplication process. These studies are relevant to both basic and applied cancer research toward understanding the roles of centrosome amplification in tumorigenesis. The selective pharmacological perturbation of mitosis has proven to be a successful chemotherapeutic target. These positive results suggest that further research into the proteins necessary for the mechanics of mitosis and, more specifically, centrosome duplication, are critical for developing future targets for cancer. The goal of this work is to determine the molecules and their role in centriole duplication in the ciliated protozoan, Tetrahymena, with the intention of designing future studies that will be applied to human systems.