Analysis Tools
behavior/neurological
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• at 3 months of age, homozygotes fail to respond with a Preyer's reflex to a 20 kHz tone burst
• however, no overt behavioral vestibular phenotype is observed
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hearing/vestibular/ear
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• homozygotes exhibit defects in hair-bundle structure that are first apparent in IHCs at P1
• by P8, defects in hair-bundle structure become more pronounced and are readily observed on both IHCs and OHCs
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• at P1, homozygotes display varying degrees of disorganization in the hair-bundle structure of IHCs in the basal-most regions of the cochlea, not evident at E18.5
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• remaining IHC stereocilia are often misaligned
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• many IHC stereocilia are absent
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• remaining IHC stereocilia are often fused
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• by P8, homozygotes display disorganization in the hair-bundle structure of OHCs in the basal-most regions of the cochlea
• mutant OHC hair bundles are smaller, exhibit a less distinctive V-shaped form and are more U-shaped
• mutant hair bundles fail to develop the typical broader, flatter, and wider-angled appearance of wild-type hair bundles in the basal end of the cochlea
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• OHC stereocilia are shorter than normal; however, stereocilial fusion is rarely observed
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• at 3 months of age, homozygotes show absence of hair cells in the basal, high-frequency end while the apical, low-frequency end of the cochlea appears unaffected
• hair cells are still present in the organ of Corti until at least P22; however, complete loss of hair cells is noted between P21 and P80
• in contrast, no hair cell loss is observed in the vestibular organs
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• between P21 and P80, some homozygotes exhibit a complete loss of the organ of Corti
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• close apposition of the stereocilia is noted in ruthenium red-stained preparations; however, the spacing of stereocilia appears normal in the absence of ruthenium red
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• at P21, homozygotes exhibit complete absence of shaft connectors (defined as dense particles plus stalks), from the extrastriolar hair bundles of the utricular macula
• however, the stereocilia forming the hair bundle are not splayed
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• basal-coil OHCs obtained from homozygotes (aged P5-P7) show a reduction in mechanoelectrical transducer current amplitudes relative to heterozygotes, most likely due to the loss of stereocilia
• however, the shape of transducer currents, fast, submillisecond adaptation and slow adaptation at both the onset of excitatory and the offset of inhibitory stimuli, and the resting transducer current at hyperpolarized and depolarized potentials, remain normal
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nervous system
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• homozygotes exhibit defects in hair-bundle structure that are first apparent in IHCs at P1
• by P8, defects in hair-bundle structure become more pronounced and are readily observed on both IHCs and OHCs
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• at P1, homozygotes display varying degrees of disorganization in the hair-bundle structure of IHCs in the basal-most regions of the cochlea, not evident at E18.5
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• remaining IHC stereocilia are often misaligned
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• many IHC stereocilia are absent
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• remaining IHC stereocilia are often fused
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• by P8, homozygotes display disorganization in the hair-bundle structure of OHCs in the basal-most regions of the cochlea
• mutant OHC hair bundles are smaller, exhibit a less distinctive V-shaped form and are more U-shaped
• mutant hair bundles fail to develop the typical broader, flatter, and wider-angled appearance of wild-type hair bundles in the basal end of the cochlea
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• OHC stereocilia are shorter than normal; however, stereocilial fusion is rarely observed
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• at 3 months of age, homozygotes show absence of hair cells in the basal, high-frequency end while the apical, low-frequency end of the cochlea appears unaffected
• hair cells are still present in the organ of Corti until at least P22; however, complete loss of hair cells is noted between P21 and P80
• in contrast, no hair cell loss is observed in the vestibular organs
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• close apposition of the stereocilia is noted in ruthenium red-stained preparations; however, the spacing of stereocilia appears normal in the absence of ruthenium red
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• at P21, homozygotes exhibit complete absence of shaft connectors (defined as dense particles plus stalks), from the extrastriolar hair bundles of the utricular macula
• however, the stereocilia forming the hair bundle are not splayed
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• basal-coil OHCs obtained from homozygotes (aged P5-P7) show a reduction in mechanoelectrical transducer current amplitudes relative to heterozygotes, most likely due to the loss of stereocilia
• however, the shape of transducer currents, fast, submillisecond adaptation and slow adaptation at both the onset of excitatory and the offset of inhibitory stimuli, and the resting transducer current at hyperpolarized and depolarized potentials, remain normal
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