Each vestibular sensory epithelium in the inner ear is divided morphologically and physiologically into two zones, called the striola and extrastriola in otolith organ maculae, and the central and peripheral zones in semicircular canal cristae. We found that formation of striolar/central zones during embryogenesis requires Cytochrome P450 26b1 (Cyp26b1)-mediated degradation of retinoic acid (RA). In Cyp26b1 conditional knockout mice, formation of striolar/central zones is compromised, such that they resemble extrastriolar/peripheral zones in multiple features. Mutants have deficient vestibular evoked potential (VsEP) responses to jerk stimuli, head tremor and deficits in balance beam tests that are consistent with abnormal vestibular input, but normal vestibulo-ocular reflexes and apparently normal motor performance during swimming. Thus, degradation of RA during embryogenesis is required for formation of highly specialized regions of the vestibular sensory epithelia with specific functions in detecting head motions.
Each vestibular sensory epithelia of the inner ear is divided into two zones, the striola and extrastriola in maculae of otolith organs and the central and peripheral zones in cristae of semicircular canals, that differ in morphology and physiology. We found that formation of striolar/central zones during embryogenesis requires Cytochrome P450 26b1 (Cyp26b1)-mediated degradation of retinoic acid (RA). In Cyp26b1 conditional knockout mice, the identities of the striolar/central zones were compromised, including abnormal innervating neurons and otoconia in otolith organs. Vestibular evoked potentials (VsEP) in response to jerk stimuli were largely absent. Vestibulo-ocular reflexes and standard motor performances such as forced swimming were unaffected, but mutants had head tremors and deficits in balance beam tests that were consistent with abnormal vestibular input. Thus, degradation of RA during embryogenesis is required for patterning highly specialized regions of the vestibular sensory epithelia that may provide acute feedback about head motion.
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