Proteogenomics of Splicing Proteinopathies in Neurodegeneration - PROJECT SUMMARY/ABSTRACT: Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder that affects approximately 6.9 million Americans. Despite extensive research and significant investment in developing therapeutics, there is currently no cure for AD. It is thus urgent to accelerate research efforts to develop effective treatments. A common feature of AD pathology is the deposition of protein aggregates (proteinopathy). Identification of these aggregated proteins, along with genetic studies, can provide crucial insights into the molecular pathogenesis of AD and AD-related dementias (ADRD). This proposal is founded on recent insights from our comprehensive proteomic analyses of human brain samples, and subsequent in vivo mouse modeling. In addition to known proteinopathies (Aβ, tau, α-syn, and TDP-43), we have recently identified the aggregation of U1 small nuclear ribonucleoprotein (U1 snRNP), notably the U1-70K subunit and its N-terminal 40 kDa fragment (N40K). We have also discovered that the spliceosome pathway is the most enriched pathway in the AD aggregated proteome. Transcriptomic profiling of human brain tissues has consistently revealed reproducible, aberrant RNA splicing events in several AD cohorts compared to matched controls. We further demonstrated a causative role of U1 snRNP dysfunction in neurodegeneration using transgenic mice (N40K-Tg), which recapitulates N40K insolubility, erroneous splicing events, neuronal degeneration, and cognitive impairment. Crossing N40K-Tg with the 5xFAD amyloidosis model shows that RNA splicing dysfunction synergizes with the amyloid cascade to deregulate synaptic proteins and enhance cognitive decline. These findings support our central hypothesis that U1 snRNP proteinopathy-mediated RNA splicing dysfunction is a key event in AD pathogenesis. Building on our previous research, we aim to systematically characterize U1 snRNP and other proteinopathies (e.g., Aβ, tau, α-syn, and TDP-43) along with splicing dysfunction in AD/ADRD using human brain specimens, mouse models and human iPSC-based 2D neuron and 3D brain organoid models. We will employ the latest bulk and single cell type multi-omics-based proteogenomics tools. All large-scale datasets generated will be made publicly available on a unified resource website. Our results will provide crucial AD/ADRD proteogenomics resources, elucidate the interaction between U1 snRNP with other proteinopathies, and reveal mechanisms of RNA splicing dysfunction, potentially leading to novel strategies for effective AD/ADRD treatment.
