Although microRNA (miRNA) is expressed extensively in the postnatal mouse inner ear, its expression in the sensory epithelium during embryogenesis has not been well characterized. We investigated miRNA expression at E13.5 and E16.5 by microarray analysis, quantitative real-time-PCR, and in-situ hybridization. MiRNA-182, miRNA-140, miRNA-200c, and others showed distinct temporal and spatial expression patterns. MiRNA-194, whose expression in zebrafish seems to play an important role in the differentiation of the intestinal epithelium, was also expressed in the spiral ganglia of the mouse inner ear, where it may play a similar role in neuronal differentiation. Our results indicate that miRNAs are widely expressed in the developing inner ear, with more species recruited as hair cells differentiate, suggesting an important developmental role.
