Abstract
Transgenic mice provide unprecedented access to manipulate and visualize neural circuits, however, those on a C57BL/6 background develop progressive hearing loss, significantly confounding systems-level and behavioral analysis. While outbreeding can limit hearing loss, it introduces strain variability and complicates the generation of complex genotypes. Here, we propose an approach to preserve hearing by crossing transgenic mice with congenic B6.CAST-Cdh23Ahl+ mice, which maintain low-threshold hearing into adulthood. Widefield and two-photon imaging of the auditory cortex revealed that 2.5-month-old C57BL/6 mice exhibit elevated thresholds to high frequency tones and widespread cortical reorganization, with most neurons responding best to lower frequencies. In contrast, Ahl+ C57BL/6 mice exhibited robust neural responses across tested frequencies and sound levels (4-64 kHz, 30-90 dB SPL) and retained low thresholds into adulthood. Our approach offers a cost-effective solution for generating complex genotypes and facilitates more interpretable systems neuroscience research by eliminating confounding effects from hearing loss.
Significance statement Common C57BL/6 mice exhibit severe progressive hearing loss, which is a serious confound for systems-level and behavioral studies. While outbreeding to an unaffected strain can help, this is cost-prohibitive if multiple transgenes are introduced. We propose and validate a simple approach that preserves hearing in transgenic mice by crossing them with congenic B6.CAST-Cdh23Ahl+ mice. Using widefield and two-photon imaging of the auditory cortex, we demonstrate that Ahl+ C57BL/6 mice maintain robust neural responses across a range of frequencies and sound levels into adulthood. We also offer a rapid method to genotype offspring without the need to sequence. Our approach offers a cost-effective solution for generating complex genotypes while preserving hearing, thereby facilitating more accurate, reproducible, and interpretable neuroscience research.
Footnotes
Travis Babola has received funding from Blackbird Laboratories for research unrelated to the work described in this manuscript. The company had no role in the design, execution, interpretation, or publication of this study.
We thank Dr. Amit Agarwal for his helpful discussions about the Cdh23 genotyping strategy, Lillian Choi for technical assistance, and members of the Kanold laboratory for discussions and comments on the manuscript. Funding was provided by grants from the NIH (T.A.B. – NIH F32DC019842, P.O.K. - NIH RO1DC009607, P.O.K. - NIH RO1DC017785).
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