Unsupervised hierarchical clustering of the samples using the 18 differentially expressed miRNAs reveals that PD cases and controls cluster into separate groups with the exception of controls C2, C3, C7, and C13 and cases P18 and P19 . A similar pattern is observed using the principal component analysis , where the first principal component explains 84.1% of the variance and allows a clear separation of most samples according to affection status. Supporting the consistency of our results, analysis of variance revealed that the main source of variation in the expression data is the individual��s affection status , and we typically observed similar expression patterns for miRNAs derived from the same stem-loop precursor . In an effort to place these miRNA expression profiling findings into a biological context and to generate new testable hypotheses, and given that miRNAs have very few experimentally validated targets, we first performed an in silico search for predicted BAY-60-7550 cost target genes of the 18 differentially expressed miRNAs. In view of the fact that no particular target prediction software has consistently shown to be superior to all others, we used the ����Predicted Targets���� tool in the miRecords resource which integrates the results of eleven established miRNA target prediction algorithms. Six softwares generated almost all of the predicted target genes for the miRNAs of interest. These six softwares rely on very distinct principles and methods, namely near-perfect base complementarity in the ����seed���� region, evolutionary interspecies conservation, miRNA-mRNA duplex thermodynamic stability, target site accessibility, and machine learning techniques. Given that these predictions have not been experimentally validated, we opted for a stringent threshold of at least six softwares to select the predicted miRNA target genes for follow-up. In this case, seven miRNAs had no predicted target genes, and the remaining eleven miRNAs were predicted to target 662 unique genes . To Bortezomib correlate expression findings with relevant biological processes and pathways, we performed pathway analysis using the manually-curated literature-based Ingenuity Pathway Analysis database.