Regulation of alternative splicing during epithelial-mesenchymal transition

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PROJECT SUMMARY This application is being submitted in response to the Notice of Special Interest: Alzheimer’s-Focused Administrative Supplements for NIH Grants that are Not Focused on Alzheimer’s Disease, with Notice Number: NOT-AG-22-025. The overall goal for the funded parent award R35GM131876 is to investigate RNA binding protein-mediated alternative splicing regulation during epithelial-mesenchymal transition. Tauopathies are a diverse group of neurodegenerative diseases with varied presentations ranging from progressive memory loss to parkinsonism. A common tauopathy is Alzheimer’s Disease (AD), which is the primary cause of dementia worldwide. Tauopathies are characterized by the accumulation of intracellular neurofibrillary tangles (NFTs) composed of aggregates of hyperphosphorylated Tau protein. To date, there exists only one disease-modifying medication for AD treatment. The development of AD therapies that target Tau pathology are still in a nascent stage. Increasing evidence has shown that AD is driven by local inflammation in the brain. Recent findings implicated the type I interferon (IFN-I) response as a primary cause of neuroinflammation and synapse loss in AD. The IFN-stimulated gene signature is significantly enriched in murine AD models and correlated with clinical AD disease severity. Downregulating the neural IFN-I pathway restores pre-synaptic terminals and decreases plaque accumulation. Therefore, IFN-I constitutes a pivotal element within the neuroinflammatory network of AD and critically contributes to neuropathogenic processes. However, the mechanisms that stimulate neural IFN-I response remain elusive. Our lab recently discovered that hnRNPM, a ubiquitously expressed RNA binding protein (RBP), is critical for maintaining transcriptome integrity. We found that loss of hnRNPM promotes cryptic splicing. These cryptically spliced products further stimulate the IFN-I response. Interestingly, AD patient brains express decreased levels of hnRNPM. These results lead us to hypothesize that hnRNPM loss promotes AD through induction of cryptic splicing-mediated IFN-I response. We have designed two Specific Aims to test this hypothesis. In Aim 1, we will use iPSC-derived neurons from normal and tauopathy patients and examine whether hnRNPM loss stimulates IFN-I response due to cryptic splicing. In Aim 2, we will use patient iPSC-derived neurons and other established in vitro systems to determine whether loss of hnRNPM accelerates tauopathy-associated molecular phenotypes, including accumulation of Tau hyperphosphorylation and aggregation, and NFTs. Successful completion of these aims will help elucidate a novel mechanism of IFN-I activation in Tauopathy neurons governed by RNA dysregulation.