Modification and validation of a GAD-GFP mouse line without accelerated aging-related hearing loss

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Genetics

Background:

• GABAergic neurons in the inferior colliculus are vital for auditory processing.
• The Gad67-GFP mouse model aids in studying these neurons but suffers from hearing loss.
• Accelerated hearing loss limits the utility of the Gad67-GFP mouse model.

Purpose of the Study:

• To generate a Gad67-GFP mouse model with stable hearing for auditory research.
• To investigate the mechanisms of hearing loss in the original Gad67-GFP model, focusing on cochlear hair cells and ribbon synapses.
• To assess the utility of the new model in studying age-related hearing loss (presbycusis).

Main Methods:

• An 8-generation backcross of Gad67-GFP mice onto CBA/CaJ mice.
• Auditory Brainstem Response (ABR) testing to assess hearing thresholds.
• Immunostaining to confirm GAD67 promoter expression in the inferior colliculus.
• Cochlear morphological analysis to correlate with hearing thresholds.

Main Results:

• The F1 backcross mice exhibited significantly improved hearing thresholds compared to Gad67 and Swiss mice.
• Hearing thresholds in F1 mice closely resembled those of CBA/CaJ mice, mimicking human presbycusis.
• Morphological changes in cochlear structures correlated with ABR thresholds.
• F1 mice maintained GAD67 promoter expression in the inferior colliculus.

Conclusions:

• The Gad67-GFP x CBA/CaJ backcrossed mouse is a viable model for studying auditory processing and age-related hearing loss.
• This model overcomes the hearing loss limitations of the original Gad67-GFP mouse.
• The findings provide insights into cochlear mechanisms underlying hearing loss relevant to both the model and human presbycusis.