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microRNA-mediated regulation of APP expression
Abstract   Peer reviewed

microRNA-mediated regulation of APP expression

Aleister J. Saunders, Neha Patel, Basavaraj Hooli, Rudolph E. Tanzi and Lars Bertram
Alzheimer's & dementia, v 6(4S Part 8), pp S253-S253
Jul 2010
DOI: https://doi.org/10.1016/j.jalz.2010.05.826

Abstract

Background A number of studies have shown that APP over-expression, resulting from either a genomic locus duplication or alteration in the APP regulatory sequences, can lead to development of early-onset Alzheimer's disease (AD). Therefore, understanding the regulation of APP expression could provide valuable insight into the genetic basis of the disease and illuminate novel therapeutic avenues for AD. Here we test the hypothesis that APP protein levels can be regulated by microRNAs (miRNAs). Methods The 3'UTR of APP (∼1.2kb) was amplified and cloned into a luciferase vector. The effects of miRNA over-expression on APP 3'UTR binding, APP protein levels and APP mRNA levels was determined by luciferase assays, Western blot and QPCR, respectively. Results Utilizing human cell lines we previously demonstrated that brain expressed miR-106a binds to its putative target sequence in the APP 3'UTR and significantly reduces APP protein levels with no significant effect on APP mRNA levels. Here we show that five other brain expressed miRNAs not only bind to their predicted target sites in the APP 3'UTR and negatively regulate reporter gene expression but also negatively regulate APP protein levels. For all miRNA over-expressed, except one, APP mRNA levels are not altered suggesting that these miRNAs result in translational inhibition while one miRNA does result in decreased APP mRNA levels. Disruption of miRNA mediated expression regulation might lead to increased APP levels and increased disease risk. To test this hypothesis, we determined the genetic variation within the APP 3'UTR of probands from early onset familial Alzheimer's disease families linked to the APP-region on chromosome 21. We identified a rare sequence variant predicted to be located in a putative miRNA target site. Our functional data suggests that the minor allele of this variant disrupts miRNA binding to its target, resulting in potential dysregulation of APP mRNA and protein expression in vitro. Conclusions Our results demonstrate that human APP levels can be regulated by miRNAs in vitro, and that rare genetic variants within the 3'UTR of APP may alter miRNA mediated regulation of APP mRNA, thereby increasing APP levels and possibly increasing AD risk.

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