Browsing by Author "Carpinelli, Marina"

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    Anti-apoptotic gene Bcl2 is required for stapes development and hearing
    (Macmillan Publishers Limited, 2012-08-09) Carpinelli, Marina; Wise, Andrew; Arhatari, Benedicta; Bouillet, Phillipe; Manji, Shehnaaz; Manning, Michael; Cooray, Anne; Burt, Rachel
    In this paper we describe novel and specific roles for the apoptotic regulators Bcl2 and Bim in hearing and stapes development. Bcl2 is anti-apoptotic while Bim is pro-apoptotic. Characterization of the auditory systems of mice deficient for these molecules revealed that Bcl2 / mice suffered severe hearing loss. This was conductive in nature and did not affect sensory cells of the inner ear, with cochlear hair cells and neurons present and functional. Bcl2 / mice were found to have a malformed, often monocrural, porous stapes (the small stirrup-shaped bone of the middle ear), but a normally shaped malleus and incus. The deformed stapes was discontinuous with the incus and sometimes fused to the temporal bones. The defect was completely rescued in Bcl2 / Bim / mice and partially rescued in Bcl2 / Bimþ/ mice, which displayed high-frequency hearing loss and thickening of the stapes anterior crus. The Bcl2 / defect arose in utero before or during the cartilage stage of stapes development. These results implicate Bcl2 and Bim in regulating survival of second pharyngeal arch or neural crest cells that give rise to the stapes during embryonic development.
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    Vitamin D-deficient diet rescues hearing loss in Klotho mice
    (Elsevier, 2010-12-08) Carpinelli, Marina; Wise, Andrew; Burt, Rachel
    Klotho-deficient mice exhibit a premature aging syndrome, a feature of which is mild hearing loss. In the present study, the hearing phenotype of Klotho mice was characterized to better determine how well this phenotype resembles presbycusis in humans. It was demonstrated that Klotho animals have auditory-evoked brainstem response (ABR) threshold shifts of 14e18 dB in response to pure tone stimuli of 4, 8, 16 and 32 kHz, and similarly, in response to clicks; however, cochlear histology and spiral ganglion neuron density appeared normal in these mice. It was further demonstrated that a vitamin D-deficient diet normalizes serum calcitriol (1,25(OH)2D3) levels and prevents hearing loss in Klotho mice. It is concluded that hearing loss in Klotho mice is caused by elevated renal 1a-hydroxylase expression and consequent excessive production of calcitriol. These findings implicate the vitamin D metabolic pathway in hearing loss and pose questions as to the mechanism by which elevated calcitriol levels mediate such hearing loss.