Project Summary/Abstract Alzheimer’s Disease (AD) is the leading cause of dementia, and currently affects nearly 50 million people worldwide. The pathological hallmarks of AD are the aggregation of amyloid-ß (Aß) plaques, the formation of neurofibrillary tangles (NFT) comprising of aggregated hyperphosphorylated TAU protein, and increased neuroinflammation. Despite AD being one of the most highly funded diseases by the NIH, there is a lack of understanding in how these hallmarks contribute to disease progression. Furthermore, there have been no disease modifying treatments developed for AD. Many of these failed therapeutics involved the singular targeting of the pathological hallmarks of AD. Identifying targets within an overlapping pathway/mechanism related to Aß, tau and chronic neuroinflammation could yield more promising results in terms of developing therapeutics. Previously, it has been shown that reduction of micro-RNA-33 (miR-33) dramatically reduces Aß levels in an amyloid mouse model. miR-33 regulates the expression of many genes relating to both cholesterol homeostasis and inflammatory pathways. Intriguingly, neuronal cholesterol dysregulation and chronic inflammation are implicated in tau pathology, independent of Aβ. The goal of this proposal is to understand the functional consequences miR-33 deletion on tau pathology. To study the role of miR-33 deletion in tau pathology, we will inject miR-33 wildtype or miR-33 knockout mice with an AAV expressing a pathogenic human form of tau. We will then compare the extent of tau pathology between the wildtype and the miR-33 knockout mice. To elucidate the precise mechanisms in which miR-33 regulates tau pathology, we will generate primary cell cultures from either miR-33 wildtype or miR-33 knockout mice. We will then transduce these cells with AAV expressing pathogenic human tau to generate an in vitro Tauopathy model. The overall hypothesis of this proposal is that deletion of miR-33 will ameliorate tau pathology. To achieve the goals of this proposal, we will determine the effect of miR-33 deletion on inflammation and pathological changes in tau, including hyperphosphorylation and formation of NFTs by employing western blot analysis, immunohistochemistry (IHC), and ELISA based assays in our Tauopathy mouse model. Furthermore, we will assess the effect of miR-33 deletion on the anxiety like behavior and deficits in learning and memory observed in this Tauopathy mouse model. To determine the cell-type specific context of miR-33 reguation of tau pathology, we will perform mass spectrometry on brain tissue from our mouse model to determine the effects miR-33 deletion has on whole proteome changes. To determine the cell-type specific regulation of miR-33 on tau pathology, we will generate neuronal and microglial in vitro Tauopathy models. We will utilize western blot analysis, IHC, and ELISA based assays to determine changes in inflammatory response as well as proteopathic changes in tau Upon co...