MiR-15/107 microRNAs are important genetic regulators in Alzheimer disease

A particular group of miRNAs, which we designated the ¡§miR-15/107 gene group¡¨, may be of central relevance to Alzheimer¡¦s disease (AD) biology. This is a group of ten mature miRNAs of which multiple are highly expressed in human brain and dysregulated in AD. Our long-range goal is to develop therapeutic strategies based on miRNA neurochemistry. As a prerequisite to achieving these therapies, we need to better understand basic aspects of how the miR-15/107 genes are regulated in human cells. Specifically, we need more comprehensive data on ¡§upstream¡¨ stimuli that cause altered miRNA expression, paired with high-throughput identification of their miRNA targets. We hypothesize that miR-15/107 dysregulation will interact with metabolic and genetic factors that also alter AD risk. Methods: We have used both tissue culture experiments and human brain tissue to test the signaling pathways involved with miR-15/107 miRNAs. These have included miRNA microarrays, qPCR experiments, and various tissue culture assays designed to assess the upstream regulators and downstream targets of miR-15/107 miRNAs. Results: „h Specific Aim #1: Characterize how miR-15/107 gene expression is altered by specific AD-relevant signaling pathways. These hypothesis-based studies in cultured brain cells will be anchored in our preliminary results finding that glucose levels and other discrete experimental stimuli strongly and specifically alter miR-15/107 gene expression. We also perform comprehensive miR-15/107 expression profiling in human brain to understand how parameters linked with AD risk alter miR-15/107 gene expression because these studies need to be anchored in human brain data. The outstanding research infrastructure at the University of Kentucky Alzheimer¡¦s Disease Center (UK-ADC) brain bank, of which the PI is director, allows us to correlate the miR-15/107 expression data with clinical and genetic characteristics. „h Specific Aim #2: Characterize how miR-15/107 genes alter ¡§downstream¡¨ mRNA targets. Using methods that were developed and optimized in our laboratory, we will perform comprehensive analyses of miR-15/107 miRNA targets, and similar analyses for targets of other miRNAs implicated in neuro-degenerative diseases. Preliminary data indicate that miR-15/107 genes may be a key mechanistic link between metabolic changes and increased tau phosphorylation in human brains because CDK5 and PKA tau kinases are de-repressed by miR-15/107 miRNA downregulation. We will perform anti-Argonaute RIP-Chip analyses after miRNA transfection in cultured cells to provide the most systematic experimental assessment of the targets of miRNAs implicated in AD pathogenesis. „h Specific Aim #3: In primary cultured brain cells, assess how ¡§off-target¡¨ effects of miRNAs can be manipulated using sequence modifications. Primary cultured neurons will be transduced with lentivirus vectors harboring altered sequences related to miR-15/107 genes. We have already generated miRNA expressing lentivirus and transduced primary cultured neurons to help optimize the potential impact of miRNA-like therapies in the brain. The overall goal is to produce reagents with optimal ¡§on-target¡¨ and minimal ¡§off-target¡¨ impact to maximize the potential value of small RNA-based therapeutics. Conclusions: The miR-15/107 gene group comprises highly-expressed brain miRNAs whose functions are still largely unknown. However, we note that these genes appear to connect known upstream metabolic changes with downstream pathologies and we ultimately hope that these impactful small RNAs could represent a potential therapeutic target.