Glaucoma is a common disease of the optic nerve that affects over 60 million people worldwide and is a leading cause of blindness and visual disability in the United States. However, the biological pathways that lead to glaucoma are not well understood, and this has hindered efforts for early detection and treatment of this condition. Consequently, there is great need to clarify the causes of glaucoma at the molecular level. We identified a new glaucoma gene, TANK binding kinase 1 (TBK1) and discovered that duplication of the TBK1 gene is associated glaucoma. TBK1 has been studied extensively in non-ocular tissues and has well- defined roles in the innate immune system. Activated TBK1 stimulates assembly of a phagosome and engulfment / elimination of bacteria, proteins, and organelles (a process known as autophagy). Three autophagy genes (TBK1, OPTN, and TLR4) encode interacting proteins and have also been described as NTG genes. Moreover, autophagy has been implicated in the retinal ganglion cell death in experimental animal models of glaucoma. Our discovery that TBK1 is an NTG gene provides additional evidence that autophagy has an important role in the pathogenesis of NTG. The convergence of data from human genetic studies of NTG and from experimental glaucoma model systems provides strong evidence that autophagy may be a central process in the pathogenesis of retinal ganglion cell death in glaucoma. Our central hypothesis is that TBK1 influences autophagy at the key site of pathology in glaucoma, the retinal ganglion cells that form the optic nerve. Dysregulation of this pathway (e.g. by duplication of TBK1) may start a cascade of events that leads to apoptosis of the retinal ganglion cells, vision loss, and glaucoma. We propose to test our hypothesis with three specific aims that use our unique and powerful collection of glaucoma patient cohorts, human donor eyes, and transgenic TBK1 mice that have the same genetic defect as human patients. We will identify new genes that cause glaucoma by testing large cohorts of glaucoma patients for mutations in autophagy genes using next generation DNA sequencing strategies. We will determine the effect of TBK1 mutation (gene duplication) on the development of glaucoma and activation of autophagy in the retina of transgenic TBK1 mice (which we have made and are ready to study). We will also test drugs that stimulate or block autophagy for their ability to prevent glaucoma in these mice. We will investigate the pathway(s) by which TBK1 defects lead to glaucoma by identifying interacting proteins in the retina. With these experiments, we will begin to characterize the biological pathway by which defects in the TBK1 gene lead to glaucoma, validate an animal model of glaucoma, and begin to translate our discoveries into new approaches to diagnosis and treatment of disease.
Recently, we discovered that defects in the gene TANK binding kinase 1 (TBK1) can cause glaucoma, a common optic nerve disease that is a leading cause of blindness and visual disability in the United States. We have proposed a series of experiments using large cohorts of glaucoma patients, human donor eyes, and transgenic mice to 1) elucidate the biological pathway by which defects in TBK1 lead to glaucoma and to 2) test drugs for their ability to interfere with this cascade of events. These experiments will facilitate improved diagnosis of glaucoma;facilitate more accurate prognosis;and provide key insights into the development of novel sight-saving interventions for glaucoma.