Strial dysfunction in a melanocyte deficient mutant rat (Ws/Ws rat)

Area of Science:

• Genetics
• Otolaryngology
• Developmental Biology

Background:

• A novel homozygous mutant rat at the white spotting (Ws) locus presents a melanocyte deficiency.
• This genetic mutation offers a unique model for studying the interplay between melanocytes and inner ear function.

Purpose of the Study:

• To investigate the functional and morphological characteristics of the inner ear in the Ws/Ws rat.
• To determine the underlying causes of hearing impairment in this specific rat model.

Main Methods:

• Auditory brainstem response (ABR) testing was employed to assess hearing thresholds.
• Endocochlear DC potential (EP) measurements evaluated inner ear electrical activity.
• Electron microscopy was utilized to examine the fine structure of inner ear tissues, particularly the stria vascularis and organ of Corti.

Main Results:

• Ws/Ws rats demonstrated significantly elevated ABR thresholds, indicating severe hearing loss compared to control rats.
• Electrophysiological recordings revealed minimal to absent endocochlear potential (EP) in Ws/Ws rats.
• Morphological analysis showed a thin, flattened stria vascularis with poor marginal cell interdigitation and absent intermediate cells in Ws/Ws rats.
• The organ of Corti remained morphologically intact in both mutant and control rats.

Conclusions:

• The Ws/Ws rat exhibits profound hearing loss attributable to strial dysfunction.
• The observed strial abnormalities in Ws/Ws rats are the primary cause of their auditory impairment.
• This mutant rat serves as a valuable model for investigating the role of stria vascularis in hearing and melanocyte development.