Most animal and plant cells contain a network of small, tube-like structures, aptly named microtubules, that are involved in a variety of cell functions, including organization of cell components, transport within cells, and cell division. While microtubules in most cells have the same diameter (approximately 25 nm), some specialized cell types contain microtubules with different diameters. Cells implicated in mechanosensation in C. elegans, for example, regulate microtubule diameters to be 40% larger than microtubules in other cells in the same organism. One functional property of microtubules is their stiffness or rigidity. Physical theory predicts that large diameter microtubules should be substantially more rigid than small diameter microtubules. This research seeks to understand whether the mechanical properties (stiffness or rigidity) of microtubules with different diameters are significant enough to play a role in different biological functions. In particular, this work will measure the rigidity and diameter of single microtubules with very high precision to determine whether mechanical differences between microtubules with different diameters outweigh mechanical variations of microtubules with the same diameter. If so, the increased rigidity of large diameter microtubules is a candidate for biological function; if not, the heterogeneity of microtubule rigidities suggests that microtubule diameter is regulated for a non-mechanical purpose.
The research involves development of new light microscopy tools capable of following single molecules with nanometer precision as these molecules move through millimeter distances. While these tools will be developed to address the question of microtubule rigidity, they have applications beyond this work, potentially including long-distance cell motility and intracellular transport.
Broader Impact The project will provide research experiences, scientific authorship, and presentation opportunities for undergraduates over three years, both during the summer and academic year. Students from the physical sciences and life sciences will work together, with an eye to developing a disseminatable model of interdisciplinary research at the undergraduate level. Because of Lawrence University's increasing minority enrollment (153% increase since 2000) and PI's record of mentoring women students, this research will positively impact the engagement of underrepresented groups in the PhD pipeline. The experimental apparatus developed will also be used to recruit promising high school students to the LU Physics and Biochemistry programs.
