Progressive hearing loss in <i>Enpp1</i>^{<i>asj/asj</i>} mice.

<p>ABR threshold means are shown for <i>Enpp1</i>^{<i>asj/asj</i>} mice and littermate control mice, tested at the ages of 3 (n = 6 mutant ears/8 control ears), 6 (n = 10/10), 8 (n = 6/6), 12 (n = 22/16), 18 (n = 8/6), 26 (n = 10/8), and 30 (n = 12/14) weeks. Starting from 6 weeks of age, the mutant mice exhibit significantly higher mean ABR threshold values at all the stimulus frequencies tested (click, 8 kHz, 16 kHz, 32 kHz) compared to those of the littermate controls. Thresholds of mutant mice continue to increase with age and by 18 weeks most of the <i>Enpp1</i>^{<i>asj/asj</i>} mice are profoundly hearing impaired. The increase in 32 kHz ABR thresholds of the control mice is due to the B6 background, a strain known to exhibit age-related hearing loss starting at high frequencies. Error bars indicate standard errors of the mean.