Role of microRNA-18a in the development of inner ear

Objective: The developmental process of vertebrate inner ear is complex. MicroRNAs (miRNAs) have been reported to be involved in the development of inner ear. The current study was designed to explore the potential role of miR-18a in the development of inner ear. Methods: The expression of miR-18a and lysine demethylase 5B (Kd5mb) in inner ear tissues and house Ear Institute-Organ of Corti 1 (HEIOC1) cells was detected by miRNA in situ hybridization (MISH) and immunofluorescence (IF), respectively. TargetScane was used to predict the potential target genes of miR-18a. Luciferase reporter assay, real-time PCR, and Western blot were performed to confirm that Kdm5b is a target gene of miR-18a. In addition, the effects of miR-18a aberrant expression on H3K4me3 level were detected by Western blot. Results: The results showed that the expression of miR-18a was gradually increased and the expression of Kdm5b was gradually decreased during the inner ear development. Kdm5b was confirmed as a target gene of miR-18a and was negatively regulated by miR-18a. Moreover, the results showed that the expression of H3K4me3 was enhanced by miR-18a mimic but weakened by miR-18a inhibitor. Conclusion: This study provides evidence that miR-18a and Kdm5b was dynamically regulated in the developmental process of inner ear. The effects of miR-18a on the inner cell development might be by directly targeting Kdm5b and indirectly regulating H3K4me3.