ROLE OF MICRORNAS IN ALZHEIMER'S DISEASE (AD)

Abstract

MicroRNAs (miRs) are small non-coding RNA molecules that regulate gene expression. Circulating miRs in the plasma are very stable and are being explored as early-onset biomarkers to detect AD. Indeed, several studies have shown miR changes in AD patients (J Alzheimers Dis.2008May;14(1):27–41) rTg4510 mouse line overexpressing human P301L Tau only in the forebrain is a great animal model to examine miR changes resulting from forebrain Tau overexpression. RNA Deep Sequencing using Illumina platform (LC Sciences) was performed on hippocampus tissue and plasma samples at presymptomatic (2M: 3 littermate-pairs) and symptomatic (6M: 2 ctrls and 4 Tau) age. Bioinformatics analysis including differential miR expression, target analysis using Targetscan, miRanda and PITA, and pathway analysis was performed by AccuraScience. qPCR was performed using Taqman assays (Life Technologies). mRNA deep sequencing was performed on hippocampus tissue (2M: 3littermate-pairs) at IUSM. For plasma, at 2M, 3 miRs were significantly upregulated and 5 miRs were downregulated and at 6M, 7 were significantly upregulated and 8 were downregulated (Tau vs Ctrl, P value <0.05). In the hippocampus, at 2M, 34 miRs were significantly upregulated and 101 miRs were downregulated and at 6M, 42 were significantly upregulated and 52 were downregulated (Tau vs Ctrl, P value <0.05). Target prediction by Targetscan, miRanda and PITA for differentially regulated miRs shows for plasma (2M: 463 up, 626 down; 6M: 112 up, 2501 down) and for hippocampus (2M: 34 up, 220 down; 6M: 399 up, 335 down). Several miRs identified by deep sequencing including miR219–5p and miR150 were validated at additional time points (Postnatal-day 15, 1M, 2M and 6M) and increased animal number (n=6–9) with qPCR. Several predicted target changes were also confirmed with qPCR. Currently, we are analyzing the expression of in-silico targets of altered miRs in 2M hippocampi of Tau mice by mRNA deep sequencing. Pathway/network analysis will be conducted using DAVID and Diana-miRPath. New pathways were identified from target prediction of miRs including chemokine signaling pathway. More information will be acquired with mRNA deep sequencing validation. The clinical relevance of this study will be examined by using human plasma samples from ADNI.