PROJECT I: “Pathological α-Synuclein Transmission and Strains” PROJECT LEADER: VIRGINIA M.-Y. LEE Project I Summary/Abstract Project I, formerly Project III, is renumbered as Project I to improve the flow of the Projects in our re-submitted new U19 grant entitled “Center On Alpha-synuclein Strains In Alzheimer Disease & Related Dementias” at the University of Pennsylvania (Penn) Perelman School of Medicine (PSOM) to test the transmission and strain hypotheses of a-synucleinopathies. Dementia with Lewy bodies (DLB), Parkinson's disease (PD) without and with dementia (PDD), referred to here as Lewy body (LB) disorders (LBD), all share LB and Lewy neurite (LN) intra-neuronal pathology comprised of aggregated α-synuclein (aSyn). LBD, PDD and Alzheimer's disease (AD) with (AD+aSyn) or without LBs (AD-aSyn) are the most common aging related dementias. Moreover, LBD, AD+aSyn and multiple system atrophy (MSA), characterized by misfolded aSyn in glial cytoplasmic inclusions (GCIs), are the major neurodegenerative synucleinopathies. This diversity of clinical features and aSyn neuropathology in brains of neurodegenerative disease patients provides indirect support for the strain hypothesis wherein pathological aSyn adopts different conformations or strains that account for clinical and pathological heterogeneity between these disorders. Further, we propose the transmission hypothesis of aSyn strains to explain the variability in progression of LBD, AD+aSyn and MSA. However, both hypotheses need rigorous testing. Recently Project I and II investigators collaborated to demonstrate that intrastriatal injections of recombinant aSyn preformed fibrils (PFFs) into wildtype (WT) mice induced the templated misfolding and aggregation of endogenous aSyn that spread progressively across the striatal connectome to form PD-like LBs and LNs followed by dopaminergic (DA) neuron loss in the substantia nigra pars compacta (SNpc) and motor impairments characteristic of PD. Our key observations have been validated by many other laboratories and extended to rats and non-human primates (see preliminary non-human primate data in Project II) thereby supporting the transmission hypothesis. These confirmatory studies also showed that these novel models recapitulate LBD pathogenesis and will facilitate LBD research. We also have identified distinct aSyn strains with different conformations and biological activities through the serial in vitro propagation of synthetic aSyn PFFs generated from recombinant aSyn and we have isolated distinct human LBD, AD+aSyn and MSA aSyn strains from LBD and AD+aSyn, as well as MSA brains characterized genetically and neuropathologically by Core C from patients followed by Core B and studied clinically in Projects III and IV thereby collaboratively linking all U19 Projects and Cores. These studies defined distinct aSyn strains from AD+aSyn and LBD brains designated as aSyn-LB (LB+LN) and from MSA brains designated as aSyn-GCI. These and other prelimin...