The first study that highlighted the link between miRNAs dysregulation and PD onset was performed by Kim et al. They reported that mice with a deletion of Dicer (the enzyme that cleaves the microRNA precursors into the functional miRNA duplex) had a progressive loss of midbrain DA neurons accompanied by a reduction of mobility, suggesting that Dicer is fundamental for DA neuron differentiation and maintenance [21]. The gene discussed is DICER1; the disease is Parkinson disease.