Randall Platt

Grantee Type:
Home Institution:
University of Utah
Host Country, Institution:
United Kingdom, Imperial College of London
Project Title:
Investigating the Role of Substrate Sti ness on Beta-Catenin Activation in Osteoblasts
Project Abstract:
After finishing my undergraduate education I was unsure of what area of bioengineering I wanted to devote my future to and also, by extension, what graduate school would be best suited. The Whitaker program was an ideal solution because the opportunities it provided informed my choices and also allowed me to accomplish another longstanding goal, living abroad. Upon careful consideration of many labs in different areas I ultimately decided to join Professor Molly Stevens? lab at Imperial College London because it would enable me to conduct unfamiliar, interesting research in a pioneering lab while living in an exciting city. I enrolled in a Masters of Philosophy research scheme and undertook a project to investigate how mechanical microenvironments influence cell behavior. Cells are infinitely complex units which can sense a myriad of different attributes of their microenvironment, both soluble and non-soluble. An entire field has emerged from basic observations of how physical cues can direct cellular processes, such as, proliferation, migration, spreading, apoptosis, and differentiation. Furthermore, the hierarchal organization of tissue is also largely influenced by mechanical, in addition to chemical, cues. Although many important observations have been made, still little is known about the fine molecular events regulating these processes. My grant project was aimed at understanding how cells, specifically osteoblasts, transduce and respond to chronic mechanical stress. To accomplish this I first had to develop a materials platform that would allow for chronic mechanical stimulation while enabling reproducible and scalable screens, which are ideal for cell signaling studies. Therefore, I adapted a widely used and established protocol for chronic mechanical stimulation which uses extracellular matrix (ECM)-coated poly-acrylamide gels of tunable mechanical stiffness. Using this platform I examined the influence of substrate elasticity on ?-catenin signaling, an important pathway involved in cell-cell adhesion junctions, canonical Wnt signaling, differentiation, and cancer. Evidence to support the hypothesis that ?-catenin is ?mechanosensitive? arises from studies where acutely stressed osteoblasts show a rapid and transient increase in both the total and active form of ?-catenin. The active form of ?-catenin acts as a transcription factor for Wnt related genes while the total pool is constitutively degraded, sequestered, or ejected from the cell in order to maintain low levels of protein expression. During my grant tenure I discovered that the amounts of total and active ?-catenin are dependent on cell density, ECM coating density, time in culture, and chronic mechanical stress. With the remaining time of my grant tenure I will probe the mechanism of action behind these observations. I predict to find that multiple pathways will be involved, namely integrin, GSK-3?, and caveolin, which in combination contribute to the complex and diverse behavior of osteoblasts. During the time in my host lab and the Whitaker program I established a network with other scientists that in the future will be my colleagues and collaborators. After my grant tenure I will pursue a PhD education at MIT in Biological Engineering and will have the assistance of an NSF GRFP fellowship and the Afayan fellowship from MIT; a set of accomplishments made easier by having the experience of the Whitaker grant. I hope to build on the discoveries during my grant tenure at MIT and subsequently continue on the academia track as a post-doctoral fellow and ultimately become a professor. If I were to advise future Whitaker program applicants, I would suggest ample time for application preparation and careful selection of a host affiliation in order to have a sensible application that shows they would take full advantage of their time abroad. In heeding my own advice, in one year I was able to make a contribution to the scientific community by advancing the ?mechanosensitive? ?-catenin hypothesis and creating a materials platform for cell signaling studies. No less important, I also established life-long connections for future collaborations.