OBJECTIVE: To develop gene expression profiles of young and old senescence-accelerated mouse (SAM) cochlea and identify genes responsible for aging-related hearing loss.
METHODS: Gene micro-array slides containing 1101 mouse genes were hybridized to cDNA micro-arrays (Atlas Glass Array Mouse 1.0) that were synthesized using total RNAs from the cochlea of 2 mounts and 12 mounts mouse. Hybridization signals were visualized with cyanine-3 fluorescent reporter molecules, and the fluorescence intensities of the images were analyzed. Real-time quantitative reverse transcription PCR (qRT-PCR) was performed to validate the micro-array results. Immunofluorescence was used to identify the located region of the protein encoding by the candidate gene in the cochlea.
RESULTS: Expression of a majority of the 1101 genes represented on the micro-array slides was not altered during aging; nonetheless, changes in the expression of 3 genes were detected between young and old mouse cochlea. RT-PCR results confirmed the changes in expression of thymosin beta4 of 3 genes examined. Through the using of immunofluorescence, it was shown that thymosin beta4 was primarily located in the tectorial membrane and the supporting cells of outer hair cell.
CONCLUSIONS: Using commercially available slide micro-arrays, the results show that aging of the mouse cochlea is associated with changes in patterns of gene expression. This analysis suggests that thymosin beta4 may play a role in aging-related hearing loss. These studies lay the foundation for future studies defining the genetic basis of aging-related hearing loss.