Glaucoma is the leading cause of irreversible blindness that is due to degeneration of retinal ganglion cells (RGCs) and their axons. Biomechanical stability of the optic nerve head (ONH) which is composed of the lamina cribrosa (LC) and peripapillary sclera (PPS) and is rich in elastic fibers, has been postulated to play an important role in maintaining normal function of RGC axons. In our previous grant cycle, stemming from our initial discovery of a glaucoma-causing mutation in a microfibril-related gene, ADAMTS10, we focused on microfibrils and established their important role in glaucoma pathogenesis. Microfibrils are primarily composed of fibrillin-1 (encoded by FBN1) and required for proper elastic fiber assembly, contributing to their biomechanical properties. Elastin undergoes crosslinking by Lysyl Oxidase Like 1 (encoded by LOXL1), another key element for proper elastic fiber formation. Mice lacking LOXL1 (Loxl1-/-) develop pelvic floor organ prolapse (POP) due to malformation of elastic fibers, demonstrating the essential role of LOXL1 in normal elastic fiber formation. Our preliminary data with Loxl1-/- mice demonstrated ocular pathologies, including abnormal biomechanics as determined by Atomic Force Microscopy (AFM) and ultrastructural changes of collagens and elastic fibers in the PPS. A landmark study discovered the association of LOXL1 genomic variants with exfoliation glaucoma (XFG) caused by exfoliation syndrome (XFS) which is a disease with systemic manifestations of elastic fiber defects, including higher prevalence of POP. The association of LOXL1 with XFG/XFS has been replicated in many populations, however, it is also recognized that while defective LOXL1 is necessary, it is not sufficient to cause disease, suggesting that other factors must be involved. We hypothesize that microfibrils are a key additional factor, in part because of their indispensable role for proper formation of elastic fibers. Our central hypothesis is that alterations in the biomechanics and structure of the ONH caused by defective elastic fibers result in RGC axon pathology. This hypothesis suggests that directly targeting biomechanical abnormalities may prove to be an effective novel treatment for glaucoma patients. To test our hypotheses, we will use our newly created double mutant (Fbn1C1039G/+/Loxl1-/-) and Loxl1-/- mice to investigate biomechanical and ultrastructural changes caused by elastic fiber defects in SA 1 and to determine the effect of these changes on RGC axon pathology relevant to glaucoma in SA 2. Based on the findings, we will test the effectiveness of targeting biomechanical abnormalities for protection against RGC axon pathology. Success of this investigation would provide mechanistic insight into the role of biomechanics of the ONH in glaucoma and, more importantly, it would lead to a much-needed novel treatment approach for glaucoma patients.