Gregory C. Rogers, PhD, is an Assistant Professor at the University of Arizona College of Medicine in the Department of Cellular and Molecular Medicine. His laboratory is located in the University of Arizona Cancer Center.
The Rogers laboratory is interested in the molecular mechanisms cells use to maintain stability of their genomes. This is medically relevant because genomic instability can promote tumorigenesis. During mitosis, cells face particular risk, as errors in chromosome segregation can lead to chromosome instability (CIN) which is characterized, in part, by an abnormal chromosome complement (known as aneuploidy). Indeed, aneuploidy promotes malignant transformation and is an underlying cause of birth defects. Mitotic spindles are used to faithfully segregate chromosomes into daughter cells and, for this to occur properly, it is critical that cells assemble spindles with a bipolar fusiform-shape. Cells control spindle shape using centrosomes, tiny organelles that nucleate the microtubule cytoskeleton and organize the two spindle poles. Normally, cells contain a single centrosome which duplicates once per cell cycle, thus ensuring that cells enter mitosis with only two centrosomes to build a bipolar spindle. Cancer cells, however, overduplicate their centrosomes, which leads to multipolar spindle formation and chromosome instability. In fact, most human tumors contain cells with elevated centrosome numbers and aneuploid genomes. Importantly, the fundamental mechanisms that cells use to control their centrosome number are unclear, nor is it understood how this regulation goes awry in cancer. His work centers on characterizing a particular pathway (the Plk4 pathway) to control the biogenesis of centrosomes. This pathway utilizes both phosphorylation and ubiquitin-mediated proteolysis as regulatory mechanisms in a complex signaling pathway to control the biogenesis of centrosomes.
The Rogers laboratory is interested in the molecular mechanisms cells use to maintain stability of their genomes. This is medically relevant because genomic instability can promote tumorigenesis. During mitosis, cells face particular risk, as errors in chromosome segregation can lead to chromosome instability (CIN) which is characterized, in part, by an abnormal chromosome complement (known as aneuploidy). Indeed, aneuploidy promotes malignant transformation and is an underlying cause of birth defects. Mitotic spindles are used to faithfully segregate chromosomes into daughter cells and, for this to occur properly, it is critical that cells assemble spindles with a bipolar fusiform-shape. Cells control spindle shape using centrosomes, tiny organelles that nucleate the microtubule cytoskeleton and organize the two spindle poles. Normally, cells contain a single centrosome which duplicates once per cell cycle, thus ensuring that cells enter mitosis with only two centrosomes to build a bipolar spindle. Cancer cells, however, overduplicate their centrosomes, which leads to multipolar spindle formation and chromosome instability. In fact, most human tumors contain cells with elevated centrosome numbers and aneuploid genomes. Importantly, the fundamental mechanisms that cells use to control their centrosome number are unclear, nor is it understood how this regulation goes awry in cancer. His work centers on characterizing a particular pathway (the Plk4 pathway) to control the biogenesis of centrosomes. This pathway utilizes both phosphorylation and ubiquitin-mediated proteolysis as regulatory mechanisms in a complex signaling pathway to control the biogenesis of centrosomes.
Angiogenic Factor Signaling Regulates Centrosome Duplication In Endothelial Cells Of Developing Blood Vessels.
Source: Blood
Regulated vascular endothelial growth factor (VEGF) signaling is required for proper angiogenesis, and excess VEGF signaling results in aberrantly formed vessels that do not function properly. Tumor endothelial cells have excess centrosomes and are aneuploid, properties that probably contribute to the morphologic and functional abnormalities of tumor vessels. We hypothesized that endothelial cell centrosome number is regulated by signaling via angiogenic factors, such as VEGF. We found that endothelial cells in developing vessels exposed to elevated VEGF signaling display centrosome overduplication. Signaling from VEGF, through either MEK/ERK or AKT to cyclin E/Cdk2, is amplified in association with centrosome overduplication, and blockade of relevant pathway components rescued the centrosome overduplication defect. Endothelial cells exposed to elevated FGF also had excess centrosomes, suggesting that multiple angiogenic factors regulate centrosome number. Endothelial cells with excess centrosomes survived and formed aberrant spindles at mitosis. Developing vessels exposed to elevated VEGF signaling also exhibited increased aneuploidy of endothelial cells, which is associated with cellular dysfunction. These results provide the first link between VEGF signaling and regulation of the centrosome duplication cycle, and suggest that endothelial cell centrosome overduplication contributes to aberrant angiogenesis in developing vessel networks exposed to excess angiogenic factors.<br><br>
Preparation Of Drosophila S2 Cells For Light Microscopy.
Source: Journal Of Visualized Experiments : Jo Ve
The ideal experimental system would be cheap and easy to maintain, amenable to a variety of techniques, and would be supported by an extensive literature and genome sequence database. Cultured Drosophila S2 cells, the product of disassociated 20-24 hour old embryos, possess all these properties. Consequently, S2 cells are extremely well-suited for the analysis of cellular processes, including the discovery of the genes encoding the molecular components of the process or mechanism of interest. The features of S2 cells that are most responsible for their utility are the ease with which they are maintained, their exquisite sensitivity to double-stranded (ds)RNA-mediated interference (RNAi), and their tractability to fluorescence microscopy as either live or fixed cells. S2 cells can be grown in a variety of media, including a number of inexpensive, commercially-available, fully-defined, serum-free media. In addition, they grow optimally and quickly at 21-24 degrees C and can be cultured in a variety of containers. Unlike mammalian cells, S2 cells do not require a regulated atmosphere, but instead do well with normal air and can even be maintained in sealed flasks. Complementing the ease of RNAi in S2 cells is the ability to readily analyze experimentally-induced phenotypes by phase or fluorescence microscopy of fixed or live cells. S2 cells grow in culture as a single monolayer but do not display contact inhibition. Instead, cells tend to grow in colonies in dense cultures. At low density, S2 cultures grown on glass or tissue culture-treated plastic are round and loosely-attached. However, the cytology of S2 cells can be greatly improved by inducing them to flatten extensively by briefly culturing them on a surface coated with the lectin, concanavalin A (ConA). S2 cells can also be stably transfected with fluorescently-tagged markers to label structures or organelles of interest in live or fixed cells. Therefore, the usual scenario for the microscopic analysis of cells is this: first, S2 cells (which can possess transgenes to express tagged markers) are treated by RNAi to eliminate a target protein(s). RNAi treatment time can be adjusted to allow for differences in protein turn-over kinetics and to minimize cell trauma/death if the target protein is important for viability. Next, the treated cells are transferred to a dish containing a coverslip pre-coated with conA to induce cells to spread and tightly adhere to the glass. Finally, cells are imaged with the researcher's choice of microscopy modes. S2 cells are particularly good for studies requiring extended visualization of live cells since these cells stay healthy at room temperature and normal atmosphere.<br><br>