Investigate if sex chromosomes and gonads influence hearing sensitivity.

Sex differences in the auditory system are a well-established phenomenon across many species. In humans, women display better hearing across most age groups and lose hearing slower as they age compared to men. While gonadal hormones have been linked to women’s greater auditory function, the molecular and cellular mechanisms causing sexual dimorphism are unclear. In this study, we utilize four core genotype (FCG) mice, which are generated by manipulating the testis-determining gene sry, to produces XXF, XYF, XYM and XXM mice. Using this unique model, we aim to investigate the role of sex chromosomes in the maintenance of normal auditory function in mice.  

Auditory brainstem response (ABR) thresholds were measured at 8, 16, and 32 kHz. ABR wave I, II, III, IV, and V amplitude and latency at 90 dB SPL were measured at 8, 16, and 32 kHz.

FCG mice show no statistical difference in ABR thresholds at 1 month of age. XXF display higher ABR wave amplitudes at I, II, and V at 16 and 32 kHz, wave III and IV at 32 kHz compared to XYM. XXF display higher ABR wave I, II, III, IV, and V amplitudes at 16 and 32 kHz compared to XYF mice. XXF mice display higher wave I, II, III, IV, and V latencies at 16 kHz compared to XYM.

Overall, the results indicate that FCG mice are a beneficial model to investigate the role of sex chromosomes and gonads within the auditory system. The findings showing sex differences in ABR wave amplitude demonstrates a potential benefit of having two X chromosomes and ovaries. This suggests a synergistic relationship between the two leading to the improved hearing sensitivity in females.