Parkinson?s disease (PD) is a devastating neurodegenerative disease characterized by motor and non-motor symptoms and a specific pathology that may originate in the gastrointestinal (GI) tract. PD pathology in the brain involves neurotoxic aggregates of alpha-synuclein and the loss of dopaminergic neurons in the substantia nigra. In the GI tract, similar alpha-synuclein pathology has been detected, even years before motor symptom onset. There is also evidence that alpha-synuclein aggregates travel via the vagal nerve from the gut to the brain, and pathological staging of the PD brain supports a GI origin. As such, pathogenic alpha-synuclein originating from the GI tract is thought to spread to the brain via vagal retrograde transport to induce nigral neurodegeneration and PD. However, what facilitates the accumulation and spread of alpha-synuclein pathology in the gut is still unknown. In this study, we ask: what are the molecular signatures in the GI tract of PD patients that enable the spread of alpha-synuclein pathology to the brain? We recently found that alpha-synuclein pathology was prevalent in the human vermiform appendix in both healthy and PD individuals. Our study demonstrated that (i) the appendix is a reservoir for pathogenic forms of alpha-synuclein and (ii) removal of the appendix substantially reduced the risk for developing PD. Importantly, this work indicates that PD and healthy individuals must differ in their ability to manage alpha-synuclein pathology. We hypothesize that a crucial difference between the PD and healthy appendix is in the control of the autophagy-lysosomal pathway ? a key pathway that mediates the degradation and spread of pathogenic alpha-synuclein. Epigenetic marks like DNA methylation effectively regulate the activity of genes in the autophagy-lysosomal pathway and is involved in the decline of autophagy with age. Our data shows that in neurons of PD brains, DNA methylation abnormalities indeed occur at autophagy-lysosomal genes, along with their transcriptional dysregulation. In this study, we will now determine whether DNA methylation abnormalities at autophagy- lysosomal genes occur in the appendix of PD patients. We will map DNA methylation at autophagy-lysosomal genes (n=665) and perform a transcriptomic investigation the PD appendix. We will also determine whether DNA methylation perturbations at autophagy-lysosomal genes are mirrored in the PD appendix and brain. Next, we will determine the age-dependent regulation of autophagy-lysosomal genes in the appendix, and whether PD patients show altered epigenetic and transcriptional patterns of aging at these genes. Together, our study will provide new insights on the mechanisms underlying alpha-synuclein abnormalities in the PD gut and pathological progression in the brain. This work will be formative for the development of early PD diagnostics and treatments directed to the accessible GI tract.
The proposed research benefits public health because it provides new insight into the biological mechanisms underlying a common neurodegenerative disorder, Parkinson?s disease. This work will determine changes in the epigenetic regulation of the autophagy-lysosomal pathway in the gastrointestinal tract of Parkinson?s disease patients, which impacts the initiation and progression of disease pathology. Thus, the proposed research is relevant to the missions of the NIH because it benefits the development of diagnostic and therapeutic applications, especially for at-risk and early stage Parkinson?s disease individuals.
