NAD+ - and EVA1-C-dependent reversal of neurological deficits is mediated by differential alternative RNA splicing in tauopathic animal models

Aberrant alternative splicing events (ASEs) are emerging as a new hallmark of aging and are linked to age-related neurodegenerative pathologies such as Alzheimer’s disease (AD). AD brains are characterized by abundant intracellular proteinaceous aggregates, including neurofibrillary tangles (NFTs). Although NAD+ and related metabolites can slow down AD progression, the effects of NAD+ on ASEs in AD remain unclear. This study investigates the relationships between NAD+ metabolism, ASEs and AD or AD-like pathologies including tauopathies using deep-learning AI-based algorithms to predict protein structures and protein-protein interactions as well as experimental tauopathy models including hTau.P301S transgenic mice and transgenic hTau[P301L] Caenorhabditis elegans. Mouse transcriptomic data were mined to detect ASEs that were differentially induced in the presence of NAD+ precursor nicotinamide riboside (NR) with specific focus on the Eva1-C locus. The results reveal that the relative abundance of Eva1-C isoforms is sensitive to both the concentration of NR and to tauopathy genotype. NAD+ abundance/metabolic status modulates ASEs and the expression of EVA1-C isoforms, which in turn regulate the interaction with the key proteins, BAG-1 and HSP70, involved in orchestrating protein homeostasis. Importantly, EVA1-C is dramatically reduced in the postmortem entorhinal cortex and hippocampal neurons from 20 Braak 5/6 AD patients compared to 20 of cognitive normal humans. Thus, this study supports the novel idea that NAD+ metabolism modulates abundance of specific mRNA isoforms, and that ASEs influence disease progression in model tauopathies and potentially AD. These results could facilitate future development of NAD+-based splice-switching therapeutics for AD. To better understand how NAD+ precursor, NR, affects the hippocampus of mice in molecular pathways, we performed RNA sequencing in the hippocampal tissue of WT and P301S mice with or without NR treatment. We found that NR changed hippocampal neural activity and homeostasis.