In the developing brain, miR-9 and miR-124 are crucial for neurogenesis and neuronal differentiation4, whereas miR-34 has been shown to regulate tau expression in cultured human neuroblastoma cells (and changes in the level of tau expression are known to link to the pathology of Alzheimer’s disease)5, 6. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.