MicroRNAs targeting Nicastrin regulate Aβ production and are affected by target site polymorphisms.

Charlotte Delay,Jean-Charles Lambert,Alice Fok,G.-Y Hsiung,Sã©Bastien S Hã©Bert,Vã©Ronique Dorval,Benjamin Grenier-Boley

doi:10.3389/fnmol.2014.00067

Abstract

Despite the growing number of genome-wide association studies, the involvement of polymorphisms in microRNA target sites (polymiRTS) in Alzheimer’s disease (AD) remains poorly investigated. Recently, we have shown that AD-associated single-nucleotide polymorphisms (SNPs) present in the 3′ untranslated region (3′UTR) of amyloid precursor protein (APP) could directly affect miRNA function. In theory, loss of microRNA (miRNA) function could lead to risk for AD by increasing APP expression and Aβ peptide production. In this study, we tested the hypothesis that Nicastrin, a γ-secretase subunit involved in Aβ generation, could be regulated by miRNAs, and consequently affected by 3′UTR polymorphisms. Bioinformatic analysis identified 22 putative miRNA binding sites located in or near Nicastrin 3′UTR polymorphisms. From these miRNA candidates, six were previously shown to be expressed in human brain. We identified miR-24, miR-186, and miR-455 as regulators of Nicastrin expression, both in vitro and under physiological conditions in human cells, which resulted in altered Aβ secretion. Using luciferase-based assays, we further demonstrated that rs113810300 and rs141849450 SNPs affected miRNA-mediated repression of Nicastrin. Notably, rs141849450 completely abolished the miR-455-mediated repression of Nicastrin. Finally, the rs141849450 variant was identified in 1 out of 511 AD cases but not in 631 controls. These observations set the stage for future studies exploring the role of miRNAs and 3′UTR polymorphisms in AD.

Highlights

The small, non-coding miRNAs function as important regulators of protein expression (Ambros, 2004)
Increasing evidence suggests that single-nucleotide polymorphisms (SNP) within miRNA target sites might contribute to disease risk
We first used the National Center for Biotechnology Information (NCBI) database to generate a list of all known SNPs located within the 3 untranslated region (3 UTR) of human NCSTN (Table 1)

Summary

Introduction

The small, non-coding miRNAs function as important regulators of protein expression (Ambros, 2004). They act by imperfect base-pairing to target messenger RNAs, leading to translational repression, degradation, or both (Pillai, 2005). Important for this action is the seed sequence, located at positions 2–8 within the miRNA sequence. It is well documented that specific miRNAs are altered in a number of neurodegenerative disorders including Alzheimer’s disease (AD; reviewed in Delay et al, 2012). Aβ peptides are the major constituents of amyloid (senile) plaques that accumulate in AD brain (Glenner and Wong, 1984)

Methods

Results

Conclusion