Synaptosomal MicroRNAs, Synaptic Damage and Cognitive Decline in Alzheimer's Disease

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Title. Synaptosomal MicroRNAs, Synaptic Damage and Cognitive Decline in Alzheimer's Disease Project summary/abstract The purpose of our study is to determine the role of synaptosomal microRNAs (miRNAs) in Alzheimer's disease (AD) progression and pathogenesis. Synapses are the most important compartments of neuron that deliver signals to adjacent neuron and maintain healthy synaptic functions of the brain. Synapse territories are composed of synaptic vesicles, synaptic proteins, mitochondria, neurotransmitters receptors, postsynaptic density protein and localized small RNAs and miRNAs. Recently, several studies identified the miRNAs enrichments at synapse, synaptic vesicles and synaptosomes. However, the role of synapse-associated miRNAs in AD progression is completely unexplored. In the first part of our study, we will identify the synaptosome-specific miRNAs that are deregulated in AD, and further, we will characterize their roles in AD progression and pathogenesis. Synaptosomal fraction will be extracted from frontal cortex region of postmortem brains from AD (n=15) and healthy controls (n=15). Total RNA will be extracted from synaptosomal fraction and processed for miRNA and mRNA sequencing. The deregulated synaptosome- specific miRNAs will be characterized in vitro using miRNA mimics and inhibitor(s) approaches and mutant APP and p-tau cDNA constructs. Impact of synaptosomal miRNAs will be studied against Aβ and p-tau induced toxicities. In second part we will determine the role of synaptosomal miRNAs in Aβ induced synaptic and cognitive dysfunction in AD. The impact of synaptosomal miRNAs will be studied on healthy neurons and AD neurons with Aβ induced toxicities. We will focus on neuronal processing, neuronal growth and network development and synaptic plasticity using APP primary neuronal cultures. Alteration of synaptosomal miRNAs expression and synaptic proteins will be studied with disease progression in APP transgenic (TG) and APP knockout (KO) mice. We will execute the synaptosome-specific miRNAs expression with various cognitive behavioral and biochemical tests in 2-, 6-, 12- and 18-month-old APP TG and APP KO mice lines relative to age-matched TG negative wild-type (WT) mice. And in third part we will study the role of synaptosomal miRNAs in phosphorylated-tau (p-tau) induced synaptic and cognitive dysfunction in AD. The impact of synaptosomal miRNAs will be studied on p-tau induced toxicity in neurons, healthy neurons processing, neuronal growth and network development and synaptic plasticity using tau primary neuronal culture. Alteration of synaptosomal miRNAs and synaptic proteins will be studied with disease progression in Tau TG and Tau KO mice. We will execute the synaptosome-specific miRNAs expression with various cognitive behavioral and biochemical tests in 2-, 6-, 12- and 18-month-old tau TG and KO mice relative to WT mice. Our study outcome will provide the answers for - 1) presence of synaptosomal miRNAs at AD synapse, 2) synaptosome- associated miRNAs linked with Aβ and p-tau pathologies in AD, 3) Overall synapse function, synaptic activity, assessment of therapeutic value of synaptosome-associated miRNAs in AD.