Analysis of miR-376 RNA cluster members in the mouse inner ear

Mutations in phosphoribosyl pyrophosphate synthetase 1 (PRPS1) are associated with a spectrum of non-syndromic to syndromic hearing loss. PRPS1 transcript levels have been shown to be regulated by the microRNA-376 genes. The long primary RNA transcript of the miR-376 RNA cluster members undergo extensive and simultaneous A → I editing at one or both of two specific sites (+4 and +44) in particular human and mouse tissues. The PRPS1 gene, which contains target sites for the edited version of miR-376a-5p within its 3'UTR, has been shown to be repressed in a tissue-specific manner. To investigate whether the transcription of Prps1 is regulated by miR-376 cluster members in the mouse inner ear, we first quantified the expression of the mature miR-376 RNAs by quantitative real-time-PCR. The spatio-temporal patterns of miR-376 expression were assessed by in situ hybridization. Finally, we examined whether A →I editing of pri-miR-376 RNAs occurs in mouse inner ear by direct sequencing. Our data showed that the miR-376a-3p, b-3p, c-3p are present in mouse embryonic inner ears and intensive expression of miR-376a-3p/b-3p was detected in the sensory epithelia and ganglia of both auditory and vestibular portions of the inner ear. In adult inner ear, the expression of miR-376a-3p/b-3p is restricted within ganglion neurons of auditory and vestibular systems as well as the cells in the stria vascularis. Only unedited pri-miR-376 RNAs were detected in the cochlea suggesting that the activity of PRPS1 in the inner ear may not be regulated through the editing of miR-376 cluster.