Mentor: Professor Gretchen Meyer
The Meyer lab seeks to understand how tissue cross-talk influences skeletal muscle contraction – in particular adipose-muscle cross-talk. We hypothesize that adipose secreted cytokines (adipokines) affect the ability of muscle to generate force in an adipose depot-specific manner. For example, adipokines from visceral adipose may impair contraction in diabetes while adipokines from brown fat improve it.
In the proposed REU project will focus on a specific adipo/myokine, follistatin, and investigate its role in muscle contraction and response to external loading. The student will perform in-vivo and ex-vivo analyses of muscle contractility, apply precision forces to the muscle to induce remodeling and then assess the adaptive response at the tissue and single cell level. While the project will be focused on mechanical manipulation and analyses, the student will also gain experience with basic molecular biology techniques such as histology, qPCR and western blotting.
Mentor: Professor Marcus Foston
Plants establish posture by continuously controlling stem/branch growth in response to mechanical stimuli (Tocquard, et al., 2014). Tension wood (TW), plant tissue especially dense and rich in certain useful molecules, forms when stem bending is sustained over growth. Identifying how plant cells perceive and remember mechanical stimulation for TW formation is important scientifically and commercially.
The student will test the hypothesis that TW arises when cell deformation is sensed by mechanoreceptors in by the cytoskeleton, plasma membrane, and cell wall, leading to sustained and remembered triggering of mechanosensitive ion channels, key plant mechanoreceptors (Haswell, et al., 2011). The student will induce TW formation in wild-type A. thaliana and mutants known to lack functional MS channel gene families (e.g., mid-1 complementing activity, MscS-Like, and AtPiezo), plants grown in advance of arrival of the REU student following Wyatt et al. (2010). Testing of the hypothesis will require sectioning, immunostaining, and optical and electron microscopy to relate mechanical loading, genetics, and cell wall morphology and composition.
Mentor: Professor Jessica Wagenseil
The Wagenseil Vascular Mechanics lab focuses on the mechanical behavior of large, elastic arteries during development and disease. One of the diseases that we study is thoracic aortic aneurysm, a major cardiovascular health problem characterized by a dilated aorta that may eventually dissect or rupture. Thoracic aortic aneurysms are characterized by degraded elastic fibers in the aortic wall. We hypothesize that degraded elastic fibers facilitate movement of cells and molecules into the aortic wall that contribute to aneurysm progression.
The student will contribute to experimental biotransport measurements and analysis of the aortic wall in mouse models of thoracic aortic aneurysms. The student will also design and test a system to scale up the biotransport experiments to larger animal models. The student may participate in interventional experiments to prevent elastic fiber fragmentation using nanoparticle delivery of a polyphenolic compound. Techniques include multiphoton microscopy and image analysis, fluid and solute transport experiments and computational models, and cell culture.
Mentor: Professor Gretchen Meyer
Muscle tissue houses 5-10 distinct populations of cells that communicate with each other and with their environment. We know that when something goes awry, as in injury or disease, this communication gets interrupted or misdirected, and cells, such as fibroblasts and adipose progenitors, forget their past training and replace healthy muscle tissue with connective tissue and fat. Yet we don’t fully understand the “language” of these cells, and this keeps us from being able to fully restore cellular interaction and tissue function in many pathologies. To understand how memory guides the interaction between muscle and fat.
The student will trace the mechanobiological responses of muscle cells as they lose homeostasis, and try to interrupt adipogenesis using a mechanical stretching protocol. Results will test the hypothesis that exercise can be optimized to affect long-term muscle homeostasis.
Mentor: Professor Ram Dixit
Mechanical signals play a major instructive role during plant cell morphogenesis and tissue patterning. In plant cells, the microtubule network that lies beneath the plasma membrane has emerged as a mechanoresponsive structure, able to dynamically change its organization is response to externally applied physical forces.
In the proposed REU project, the student will use microfluidics technology to evaluate how different magnitudes and duration of tensile and shear force affect cortical microtubule organization and cell morphology. The goal is to determine whether microtubules differentially respond to different types of mechanical stimuli. To explore the mechanisms by which mechanical stimuli affect cortical microtubules, the student will study whether the MAP65 microtubule crosslinking protein and SPR1 plus-end tracking protein are required to align microtubules along the force vector. The student will learn plant cell culture, microfluidics and fluorescence microscopy to address these research questions.
Mentor: Professor Guy Genin
Both plant and animal cells have at their periphery a relatively thin layer of a molecule that has sticky carbohydrates attached to a protein backbone. These molecules, called proteoglycans in animals and arabinogalactans in plants, shifted from solid-like to fluid-like based upon the electrochemical environment, with monovalent cations screening out stickiness and divalent cations cross-linking carbohydrates. Understanding the regulation of these molecules may provide new insight into how both plant and animal cells can adapt their microenvironment and subsequent function in response to stress.
The REU student will work to unify our understanding of how plant and animal cells can stably manipulate proteoglycan-like molecules. We developed a computational model that predicts how proteoglycan and arabinogalactan mechanics change in response to the action of proton and calcium pumps in the cell membrane. The student will track via atomic force microscopy the mechanical responses of isolated arabinogalactans in varying ionic concentrations, and evaluate how structures such as trichomes alter their mechanics via pH changes once probed mechanically. Such integrated models and experiments may uncover critical dynamics permanent, mechanically induced changes to the cell microenvironment.
Mentor: Professor Elizabeth Haswell
All organisms sense and respond to physical forces. But it is often unclear how they do so and how errors in doing so lead to changes that are remembered long enough to cause disease. Mechanosensitive ion channels, the current focus of the Haswell Lab, are found in all kingdoms of life and are involved in osmoregulation, hearing, and touch perception. Different families of mechanosensitive ion channels have been identified and studied in bacteria (MscS and MscL), plants (MSL, MCA, OSCA), and animals (TRP, Piezo).
The REU project will contribute to our ongoing comparative study of the function and regulation of mechanosensitive ion channels across kingdoms. The student will characterize mechanosensitive ion channels from multiple families in the model moss Physcomitrella patens. They will use CRISPR/Cas9 technology to disrupt the function of mechanosensitive ion channel genes and examine their subcellular localization in transient expression systems using confocal microscopy. Transient responses, interpreted through simplified models (Fig. 2), will enable characterization of time constants for memory of loading. Results will help reveal how the function of mechanosensitive ion channels has evolved in the green lineage.
Mentor: Professor Marcus Foston
Supramolecular polymer hydrogel responsive to external stimuli can be formed by inter- and intra-molecular interactions, such as hydrogen bonding. With its outstanding and diverse properties, plant-biomass derived cellulose nanocrystal (CNC) can be used as a reinforcement filler in hydrogel materials. Surface modifications of CNC can add chemical functionality that promote the strong hydrogen bond formation in response to changes in pH. Understanding how surface modification of CNCs and external stimuli (i.e., pH) affect hydrogel structural and physical properties is important to tuning the mechanical performance of CNC hydrogels
The REU project will focus on preparing CNC hydrogels via modification with different chemical reagents, including mono Boc-protected ethylene diamine, 1-glycidyl-s-triazine-2,4,6-trione, and diaminotriazine and characterizing CNC hydrogel physical, structural, and mechanical properties.
Mentor: Professor Amit Pathak
During organ development and progression of diseases such as metastatic cancer, cells migrate both singly and collectively on matrices of varying stiffness. We study how grouped cells remember matrices and use this mechanical memory to navigate matrices with heterogeneous topography and confinement.
The REU project student will fabricate hydrogels of at least two different stiffnesses using our technologies and perform experiments involving collective cell migration using breast epithelial cells and mutant cells. By analyzing time-lapse and confocal microscopy data, the student will seek to understand the spatiotemporal variation of migration and mechanotransduction markers. Experiments will show how mutants within a healthy cell population can dominate collective memory in migration. Computational models are developed to understand fundamental mechanobiology principles of mechanical memory and matrix interactions in migratory cells.
Mentor: Professor Nathaniel Huebsch
The Huebsch lab focuses on understanding why inherited mutations in contractile proteins of cardiomyocytes lead to electrical conduction abnormalities, which ultimately lead to sudden death in children. We hypothesize that mutations in contractile proteins within the sarcomere alter cardiomyocyte calcium and voltage handling, and that changes in the mechanics of the tissue environment will exacerbate this response.
The student will work with Huebsch lab team members to form arrays of cardiac micro-tissues derived from human induced pluripotent stem cells, perform high speed video microscopy of the tissues and use Matlab coding routines to convert these videos into information on tissue-level contractility, voltage and calcium handling. He/she will also assist in structural and biochemical analysis of the tissues and gain proficiency in these techniques.