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Mice heterozygous for the deafness gene have normal auditory thresholds
J P Kirsch1, M K Money, D B Webster
1Department of Otolaryngology, Head and Neck Surgery, Tulane University Medical Center, New Orleans, Louisiana.
Hearing Research
|May 1, 1993
Summary
Deafness (dn/dn) mice with a recessive mutation show cochlear degeneration. Heterozygous (+/dn) mice, however, exhibit normal hearing and cochlear morphology, indicating no adverse effects from the single recessive allele.
Area of Science:
- Genetics
- Neuroscience
- Auditory Science
Background:
- Homozygous recessive mutation in deafness (dn/dn) mice causes early postnatal cochlear degeneration.
- Heterozygous (+/dn) mice appear to have normal hearing and cochlear morphology via light microscopy and Preyer reflex testing.
Purpose of the Study:
- To investigate potential sub-clinical auditory effects in heterozygous (+/dn) deafness mice.
- To determine if the recessive deafness allele impacts hearing thresholds not detectable by standard reflex tests.
Main Methods:
- Auditory Brainstem Response (ABR) threshold measurements were compared between homozygous dominant (+/+) and heterozygous (+/dn) deafness mice.
- CBA/J mice were used as an additional control group.
- A 'generational backtracking' method was employed to increase the identification probability of homozygous (+/+) mice.
Main Results:
- No significant differences in hearing thresholds were found between heterozygous (+/dn) mice and presumed homozygous dominant (+/+) mice.
- Hearing thresholds of heterozygotes were also comparable to the control CBA/J mice.
- The study did not detect deleterious effects on hearing in heterozygotes.
Conclusions:
- The recessive deafness allele in (+/dn) mice does not appear to cause detectable hearing deficits.
- Standard auditory tests are sufficient to assess hearing in these heterozygous mice.
- Further research may explore other potential impacts of the allele not related to gross hearing function.