Characterization of the Role of Myosin 1e in the Progression of Breast Cancer and Focal Segmental Glomerulosclerosis

Abstract

Myosin 1e (myo1e) is a long-tailed class I myosin implicated in breast cancer progression and the development of focal segmental glomerulosclerosis (FSGS). This dissertation characterizes how myosin functions in these distinct pathologies. In chapter 2, I dissect the role that myo1e plays in the metastasis of breast cancer cells. Using the highly invasive 4T1 cell line, I demonstrate that cells deficient in myo1e exhibit altered morphologies and slower migration rates. Dissection of the migration defects in myo1e KO cells led us to investigate the role of myo1e in organelle trafficking, integrin endocytosis and the assembly and disassembly of focal adhesions. Our preliminary results suggest that cells deficient in myo1e exhibit reduced rate of focal adhesion disassembly. In chapter 3, I characterize three novel mutations in myosin 1e that were isolated from patients with FSGS: A92E, H506D, and G562R. Using in silico and comparative sequence analyses, I demonstrate that these mutations are likely pathogenic and highly evolutionarily conserved. Expressing these mutants in Madin-Darby Canine Kidney (MDCK) cells, I demonstrate that mutants myo1eH506D and myo1eG562R exhibit proper membrane enrichment, while the myo1eA92E mutant mislocalizes to the cytoplasm. Additional characterization of the properly localizing myo1eG562R mutant demonstrated that its junctional dynamics were not different from the junctional dynamics of myo1eWT. Taken together, our findings in chapter 3 demonstrate functional differences among myo1eA92E and myo1eH506D and myo1eG562R mutants and how these differences may contribute to their pathogenicity.