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Allele-specific miRNA mediated regulation of APP expression
Abstract   Peer reviewed

Allele-specific miRNA mediated regulation of APP expression

Aleister Saunders, Neha Patel, Basavaraja Hooli, Trisha Kadakia, Allison Caban-Holt, Peter Nelson, Rudolph Tanzi and Lars Bertram
Alzheimer's & dementia, v 8(4S Part 11), pp P421-P422
01 Jul 2012
DOI: https://doi.org/10.1016/j.jalz.2012.05.1125

Abstract

Background Increased APP expression can result in development of Alzheimer's disease. APP expression can be regulated post-transcriptionally by miRNAs. miRNAs bind to specific sequences within the APP 3' UTR to repress APP expression. Given this mechanism of regulation and the fact that increased APP levels can lead to AD development it is possible that genetic variation in miRNA target sequences may alter miRNA mediated regulation of APP levels and therefore modulate the risk of developing AD. Methods Bioinformatic tools were used to initially identify miRNA target sites within APP as well as genetic variation in the APP locus. In situ hybridization of human brain was used to confirm and localize miRNA expression. Luciferase reporter assays and Western blot analysis of human cell lines, neural progenitor cells and mouse primary corital neurons that over-expressed miRNAs, miRNA inhibitors and/or reporter constructs was used to assess miRNA mediated regulation of APP expression. Human subjects were recruited following IRB approved protocol, DNA was isolated from blood and sequencing based genotyping was utilized. Results We demonstrate that six human, brain expressed miRNAs (miR-17-5p, 106a, 106b, 153, 324-5p, and 495) repress APP expression and used in situ hybridization of post-mortem human brain tissue to confirm brain expression and localization of these six miRNAs. We identified a SNP, rs45455403, that is located just outside of the miR-495 target site seed sequence. We tested the functional consequences of this SNP's minor allele using luciferase reporter assays. Introduction of the minor allele into the 3'UTR results in elimination of miR-495 repression of APP expression observed in the wild-type 3'UTR. rs45455403 is present in 6% of the African American (AA) community and therefore we are recruiting AA patients and controls to determine if this SNP increases the risk of developing AD. Conclusions Our data demonstrates that the minor allele of rs45455403 eliminates miR-495 mediated repression of APP expression. Given the functional consequences of the minor allele of rs45455403 it is possible that this allele may alter risk of developing AD. We are in the process of testing this hypothesis.

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