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Malformation and degeneration in the inner ear of mos transgenic mice
1Department of Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston 02114.
Abstract:
Transgenic mice carrying the mos proto-oncogene linked to a retroviral transcriptional control sequence display behavioral abnormalities including circling, hyperactivity, head tilt, and bobbing. Axonal degeneration, neuronal chromatolysis, spongiform encephalopathy, gliosis, and inflammatory infiltrates are reportedly found in the central nervous systems of all mutants with the behavioral traits. Hearing was tested by means of broadband free-field rarefaction clicks with auditory brain stem response recorded between vertex and mouth electrodes. No detectable auditory response was elicited in transgenic animals, in contrast to five distinct positive peaks observed in littermate control animals. Light microscopic survey of temporal bone histopathology in mutants revealed extensive degeneration of the organ of Corti with loss of hair cells in all cochlear turns and loss of supporting cells and atrophy of spiral ganglion cells. The spiral limbus was deformed, with replacement of the usual convexity of the superior surface by a flattened trough configuration. Hair cells of the vestibular end organs appeared normal. Pathologic alteration in levels of mos transgene RNA appears to have a direct effect on the structural integrity of the inner ear.
Insights
Transgenic mice with the mos proto-oncogene exhibited severe hearing loss and inner ear degeneration. This study links mos transgene expression directly to the structural damage observed in the auditory system.
Area of Science:
- Neuroscience
- Genetics
- Otolaryngology
Background:
- Transgenic mice expressing the mos proto-oncogene exhibit neurological and behavioral abnormalities.
- These abnormalities include circling, hyperactivity, and head bobbing, accompanied by central nervous system pathology.
Purpose of the Study:
- To investigate the auditory function and inner ear histopathology in transgenic mice carrying the mos proto-oncogene.
- To determine the correlation between mos transgene expression and the observed pathological changes.
Main Methods:
- Auditory brainstem response (ABR) testing using broadband rarefaction clicks to assess hearing.
- Light microscopic examination of temporal bone histopathology, focusing on the cochlea and spiral ganglion.
Main Results:
- Transgenic mice showed no detectable auditory response via ABR, unlike control littermates.
- Histopathology revealed extensive degeneration of the organ of Corti, loss of hair cells and spiral ganglion cells, and deformation of the spiral limbus.
- Vestibular end organs appeared unaffected.
Conclusions:
- The mos proto-oncogene in transgenic mice leads to profound hearing loss.
- Pathological alterations in mos transgene RNA levels directly impact the structural integrity of the inner ear, causing sensorineural hearing loss.