Research in the So Lab

Core Applications

• Carcinogenesis
  

• Cancer is caused by the accumulation of mutations in oncogenes and tumor suppressor genes that control cell physiology and division. Mitotic recombination has been estimated to be the underlying cause of LOH 25-50% of the time (Gupta et al., 1997; Morley et al., 1990; Zhu et al., 1992). In collaboration with Prof. Bevin Engleward (BED, MIT), we will combine genetic engineering with mechanico-optical engineering to develop the technology to detect genetic instability in mammals. A transgenic mouse will be engineered to carry a fluorescent marker for identification of cells that have undergone a mitotic recombination event. A high-throughput two-photon microscope system will make it possible to quantify recombinant cells in situ in a variety of cells, to characterize the cell types most prone to mitotic recombination, and to discern the contribution of recombination events that occur in stem cells. Yet another important application will be in studying the effects of cancer chemotherapeutics on mitotic recombination and in determining how specific genetic traits effect cellular susceptibility to chemotherapy-induced mitotic recombination. It is hoped that this line of research will ultimately aid in pharmacogenomics. This new technology will be of fundamental importance in revealing genetic and environmental processes that drive cancer-promoting mitotic recombination events in mammals.

• Optical biopsy based on multi-photon imaging, spectroscopy and second harmonic generation

• Histological analysis is the clinical standard for assessing tissue health and the identification of pathological states. This analysis requires tissues to be excised, fixated, sectioned, stained and subsequently examined under a light microscope. The invasive nature of this process justifies development of a supplementary approach without excision. "Optical biopsy" is a promising alternative. Two-photon microscope allows in vivo imaging of cellular and extracellular matrix structures with sub-micron resolution inside intact 3-D tissue. While the utility of two-photon microscopy for biological studies has been clearly demonstrated in areas such as neurobiology and embryology, its clinical potential remains unrealized. In collaboration with Dr. Peter Kaplan (Unilever Edgewater Laboratory) and Dr. Christie Ammirati (Pennsylvania State University Medical School) to address this clinical need, we will develop and evaluate two-photon endoscopic systems. We will characterize the performance this device in tissue phantoms, animal models and excised human skin biopsy specimens.

• Mechanotransduction

• Mechanical stimuli regulate many cellular responses, particularly within the cardiovascular system. Understanding the process of mechanotransduction has been challenging, in part because techniques for precisely controlled mechanical stimulation have not been widely used. Under the leadership of Prof. Roger Kamm (ME and DEB, MIT), we will develop rigorous, highly specific and controllable methods of studying mechanotransduction are needed based on novel micromanipulation techniques such as magnetic trap, optical trap, and microlithography and cellular analysis tools such as two-photon microscopy and spectroscopy, fluorescence based laser tracking microrehology. In the first phase of this project, we will investigate the mechanical responses of several novel genes in smooth muscle cells and endothelial cells. This studies are highly relevant to a number of cardiovascular diseases, including hypertensive vasculopathy.

• Torsional effects on DNA-protein binding

• In collaboration with Prof. Peter Dedon (BED, MIT), we study the structural effects and enzymological consequences of positive supercoiling in DNA. Preliminary results reveal novel properties of helically over-wound DNA consistent with an increase in the flipping of nucleobases out of the helix. We propose to define the effects of positive supercoiling on DNA structure and dynamics and on the activity of base-flipping methyltransferase enzymes. Biochemical and spectroscopic characterization in combination with biomechanical and biophysical methods will be used to study the effect of positive supercoiling on DNA structure and enzyme activity These complementary approaches will provide important insights into the biological role of superhelical tension in DNA physiology, DNA damage and DNA repair.