MicroRNAs as biomarker of Parkinson disease?

Although first described in 1993,¹ microRNAs (miRNAs) have only recently emerged as important regulators of gene expression in the context of Parkinson disease (PD).² miRNAs belong to the class of small non–protein coding RNAs, which mediate the posttranscriptional gene silencing of target RNA transcripts. Specifically, miRNAs are 18- to 25-nucleotide single-stranded RNA, which can inhibit gene expression by binding to the 3′ untranslated region of target genes (figure, A). Of note, the miRNA machinery has a critical role in the biology of dopamine neurons, the predominant cell type affected by neurodegeneration in PD. When eliminating mature miRNAs by deleting Dicer, the ribonuclease required for the early steps of miRNA biogenesis (figure), a nearly complete loss of the dopaminergic neuronal phenotype is observed in a murine cellular model.³ Several subsequent studies addressed the role of miRNAs in PD pathogenesis by focusing on known PD genes and gene products, such as α-synuclein or LRRK2, and identified miRNAs specifically regulating the expression of these proteins.^4,5