Ectopic mineralization in the middle ear and chronic otitis media with effusion caused by RPL38 deficiency in the Tail-short (Ts) mouse.
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ABSTRACT: Inflammation of the middle ear cavity (otitis media) and the abnormal deposition of bone at the otic capsule are common causes of conductive hearing impairment in children and adults. Although a host of environmental factors can contribute to these conditions, a genetic predisposition has an important role as well. Here, we analyze the Tail-short (Ts) mouse, which harbors a spontaneous semi-dominant mutation that causes skeletal defects and hearing loss. By genetic means, we show that the Ts phenotypes arise from an 18-kb deletion/insertion of the Rpl38 gene, encoding a ribosomal protein of the large subunit. We show that Ts mutants exhibit significantly elevated auditory-brain stem response thresholds and reduced distortion-product otoacoustic emissions, in the presence of normal endocochlear potentials and typical inner ear histology suggestive of a conductive hearing impairment. We locate the cause of the hearing impairment to the middle ear, demonstrating over-ossification at the round window ridge, ectopic deposition of cholesterol crystals in the middle ear cavity, enlarged Eustachian tube, and chronic otitis media with effusion all beginning at around 3 weeks after birth. Using specific antisera, we demonstrate that Rpl38 is an ?8-kDa protein that is predominantly expressed in mature erythrocytes. Finally, using an Rpl38 cDNA transgene, we rescue the Ts phenotypes. Together, these data present a previously uncharacterized combination of interrelated middle ear pathologies and suggest Rpl38 deficiency as a model to dissect the causative relationships between neo-ossification, cholesterol crystal deposition, and Eustachian tubes in the etiology of otitis media.
SUBMITTER: Noben-Trauth K
PROVIDER: S-EPMC3024801 | biostudies-other | 2011 Jan
REPOSITORIES: biostudies-other
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