Identification and Characterization of MicroRNAs Involved in Parkinson’s Disease: Potential Role as Diagnostic Biomarkers.

Background. MicroRNAs (miRNAs) are small non-coding RNAs of 20-22 nucleotides, involved in transcriptional and post-transcriptional regulation of gene expression and involved in Parkinson’s disease. Objective. Identification of a suitable gene set to use as normalizers in expression analysis in PBMCs PD study. Assessment of the potential role as PD biomarker of miR-29a-3p, miR-29b-3p, miR-30a-5p, miR-30b-5p, and miR-103a-3p in PBMCs and plasma samples from L-dopa treated PD and drug-naïve PD patients. MiRNAs discovering through deep sequencing analysis and creation of in silico miRNAs target prediction. Methods. Plasma and PBMCs miRNAs from L-dopa treated PD, drug-naïve PD patients, and controls were analyzed (qRT-PCR), data normalized using RNU24/Z30 for PBMCs, and synthetic spike-in for plasma. Statistical significance of miRNA expression differences calculated by computing a two-tailed paired t-test. Illumina MiSeq NGS platform analysis was performed. MiRNA resources were combined to detect putative miRNA targets. Results. RNU24/Z30 as reliable normalizer for expression analysis in PBMCs PD study were identified. An over-expression of miR-103a-3p, miR-29a-3p and miR-30b-5p in PBMCs PD samples were found. Over-expression trend of miR-30a-5p in plasma PD samples and over-expression trend of miR-30b-5p in plasma drug-naїve PD samples were detected. NGS analysis data were not sufficient to generate meaningful biological results. A sophisticated in silico target prediction model were elaborated. Discussion. We showed for the first time an over-expression of miR-103a-3p in PD patients and replicated a documented deregulation in PD, albeit opposite to published data, of miR-29a-3p and miR-30b-5p. The trend of higher expression of miR-30b-5p in plasma drug-naïve PD samples suggested an involvement of the treatment in the plasma miRNA expression. The in silico analysis identified putative candidate target genes, including genes related to neurodegeneration and PD, such as LRRK2 for miR-30b-5p and miR-103a-3p, PARK7/DJ-1 for miR-29a-3p, Bcl-2 as common target for all miRNAs.