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All cells experience a variety of forces throughout their lifetimes. These forces are sensed by cell adhesion molecules on the cell surface that trigger the activation of downstream signaling pathways that ultimately culminates in cytoskeletal rearrangements. These rearrangements result in cell stiffening or cytoskeletal reinforcement, which is important to counterbalance the forces that the cell experiences. The force transmission pathways that cells employ are critical for normal cell and overall tissue homeostasis and when these pathways are perturbed, it can lead to diseases like cancer. There are many different proteins involved in force transmission, but how specific mutations in proteins in these pathways contribute to pathophysiology in living organisms is less understood. Therefore, it is critical to examine how inhibition of force transmission at specific sites confers a disease phenotype.In epithelial cells, epithelial (E)-cadherin is the prominent cell adhesion molecule that adheres cells to neighboring cells at structures called adherens junctions. In addition to playing a role in cell adhesion, E-cadherin is a known force sensor and transducer. E-cadherin senses force on its extracellular domain, which elicits a conformational change in its cytoplasmic domain. This conformational change triggers a signaling cascade by recruiting proteins to the adherens junctions that contribute to the propagation of the signal. One protein that is recruited to adherens junctions in response to force on E-cadherin is vinculin. During this process, vinculin is phosphorylated on tyrosine residue 822, which results in activation of the RhoA pathway and cytoskeletal reinforcement. Phosphorylation of vinculin Y822 is required for force transmission in response to force on E-cadherin, as substitution of a phenylalanine at 822 inhibits this pathway and blocks vinculin recruitment to adherens junctions. Interestingly, vinculin Y822 is mutated to a cysteine in some human cancers, suggesting that this residue is important for normal physiology. However, vinculin’s role in force transduction in a more physiological context is less understood., In this thesis, I determine that mutations at vinculin Y822 promote malignant phenotypes in cancer cells and that a phenylalanine substitution at vinculin Y822 leads to pathophysiology in an animal model. First, I demonstrate that substitution of a phenylalanine or a cysteine at vinculin 822 in breast cancer cells promotes processes such as proliferation and migration, thus increasing their malignant phenotypes. Y822C and Y822F vinculin cells have altered focal adhesion biology, with Y822C vinculin cells having numerous, small focal adhesions and Y822F vinculin cells having numerous, large focal adhesions compared to cells containing wildtype vinculin. The mechanism by which these differences occur is due to the modulation of ligand recruitment to the vinculin proteins. Y822C vinculin significantly binds to more paxillin but binds to less talin and β-actin, while Y822F vinculin binds more talin and paxillin compared to wildtype vinculin. The significant increase of paxillin binding to Y822C vinculin is in part due to a disulfide bond formation via the cysteine, as this effect is diminished with the addition of a disulfide bond reducer and an alanine or serine substitution does not result in increased paxillin binding., Furthermore, I demonstrate that a global Y822F vinculin knockin promotes pathophysiology in a mouse model. Specifically, I show that Y822F vinculin homozygous mice have an increase in body weight, visceral fat, and liver weight as they age compared to heterozygous mice. The mechanism by which this occurs is under active investigation. Taken together, this work establishes a paradigm for how mutations at vinculin Y822 contribute to disease by modulating the recruitment of its binding partners, thus altering vinculin function to promote malignancy. Additionally, this research provides a framework for understanding how Y822 vinculin is important in maintaining normal tissue homeostasis.