Downregulated miRNAs associated with auditory deafferentation and compensatory neural plastic changes following single-sided deafness in the inferior colliculi of rats.

BACKGROUND AND AIMS

Deafferentation and compensatory neural plastic changes in the inferior colliculus (IC) have been suggested following single-sided deafness (SSD). We explored related miRNA changes in the IC of SSD rats using miRNA microarray analyses.

METHODS

Eight-week-old rats were divided into control and SSD rats (n = 8 for each group). SSD rats underwent right-side cochlear ablation surgery, with the IC harvested two weeks post-surgery. miRNA microarray analysis was performed using GeneChip miRNA 4.0, microarray (Affymetrix Inc.). miRNAs whose expression levels differed between SSD and control rats with a fold-change ≥ 1.5 and P < 0.05 were examined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Target genes of differentially expressed miRNAs were predicted using TargetScan software. The pathways related to predicted target genes were analyzed. mRNA levels of predicted target genes were estimated using qRT-PCR.

RESULTS

The expression of miR-15b-5p, miR-202-5p, and miR-212-3p was lower in the contralateral (left) IC of SSD rats than that of control rats. In SSD rats, miRNA expression levels in the contralateral IC were 0.45-, 0.25-, and 0.50-fold lower for miR-15b-5p, miR-202-5p, and miR-212-3p, respectively (P < 0.05). The expression of predicted target genes (Spred1, Rasa1, Lsm11, and Srsf1) was higher in the contralateral IC of SSD rats than in control rats. The targets were predicted to be related with cleavage of growing transcripts in the termination region, mitogen-activated protein kinase family signaling cascades, RAF/AMP kinase cascade, regulation of RAS by GTPase activating proteins (GAPs), and RNA polymerase II transcription termination. For ipsilateral ICs, miR-425-3p, miR-199a-5p, and miR-134-3p showed lower expressions in SSD rats than in control rats, which were 0.55-, 0.61-, and 0.69-fold lower, respectively (P < 0.05). The expression of predicted target genes (Atp2b2, Grin2b, Foxp1, Ztbt20, Zfp91, and Strn) was higher in the ipsilateral IC of SSD rats; the regulation of synaptic plasticity, cAMP signaling pathway, metal ion binding, and calcium ion transport can be associated with these target genes.

CONCLUSION

Adult rats with unilateral auditory deprivation showed miRNA changes in the IC. The contralateral IC showed decreased miRNA expression predicted to be related to MAPK and RAS signaling, whereas the ipsilateral IC revealed decreased miRNA expression predicted to be associated with synaptic plasticity and calcium ion transport.