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Strial dysfunction in a melanocyte deficient mutant rat (Ws/Ws rat)
K Kitamura1, M Sakagami, M Umemoto
1Department of Otolaryngology, Osaka University Medical School, Japan.
Abstract:
A homozygous mutant rat at the white spotting (Ws) locus showing a deficiency of melanocytes has recently been found (4, 5). The function and morphology of the inner ear of the Ws/Ws rat were examined by auditory brainstem response (ABR), endocochlear DC potential (EP), and electron microscopy. The mean ABR threshold of the Ws/Ws rat was significantly higher than that of the control +/+ rat. Most Ws/Ws rats showed no or very little EP. In electron microscopy, the stria vascularis of the Ws/Ws rat proved to be very thin and flat with poor interdigitation of marginal cells, and absence of intermediate cells. The organ of Corti appeared to be intact in both the +/+ rat and the Ws/Ws rat. These electrophysiological and morphological findings suggest that the Ws/Ws rat suffered from severe hearing loss caused by strial dysfunction.
Insights
The white spotting (Ws) mutant rat exhibits hearing loss due to inner ear strial dysfunction. This model is crucial for understanding melanocyte deficiencies and their impact on auditory health.
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.