behavior/neurological
• homozygotes have a moderate circling phenotype, but penetrance is only approximately 35% so this is not a reliable phenotypic determinant.
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mortality/aging
N |
• Homozygotes do not display postnatal lethality
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nervous system
• additional, disorganized inner hair cells are found near the chochlear base, and the density of inner hair cells near the apex and base of the cochlea is greater than in controls, but the cochlea is shorter than normal so the total hair cell number may not be abnormal
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• homozygotes have an extra row of outer hair cells at the cochlear apex, although the cochlea is shorter than normal so the total number of hair cells may not be abnormal
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hearing/vestibular/ear
• the cochlea is smaller and shorter than that of controls
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• shorter than normal
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• additional, disorganized inner hair cells are found near the chochlear base, and the density of inner hair cells near the apex and base of the cochlea is greater than in controls, but the cochlea is shorter than normal so the total hair cell number may not be abnormal
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• homozygotes have an extra row of outer hair cells at the cochlear apex, although the cochlea is shorter than normal so the total number of hair cells may not be abnormal
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• saccule is smaller than normal and not fully separated from the utricle
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• duct connecting the saccule and cochlea is larger than normal
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• the saccule does not fully separate from the utricle
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• the saccule is smaller than normal
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• all homozygotes have hearing impairment, with ABR thresholds 20-30 dB higher than controls at one month of age and 25-45 dB higher than controls at six months of age
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