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. 2013 Mar 13;8(3):e58156. doi: 10.1371/journal.pone.0058156

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© 2013 Chen et al

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.

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(A) Results of recurrent ABR measurement (click thresholds) with age. Hearing impairment can be detected as early as 3 weeks old in Mcph1^tm1a/tm1a mice (n = 13). Hearing profile of the Mcph1^tm1a/tm1a mice showed either a stable, progressive, or fluctuating pattern with age (three of them marked dark). All the wild type (n = 13) and heterozygous (n = 17) mice displayed normal click thresholds with age. (B) Auditory chain (incus-stapes joint) and oval window sound transduction was severely impeded. Normal incus-stapes joint of auditory chain in a Mcph1⁺ ^/+ mouse, and a clear oval window is necessary for sound vibration conduction. After removing some of the amorphous material in the middle ear cavity of a Mcph1^tm1a ^/tm1a mouse, the incus-stapes joint (arrow head) and the oval window (arrow) is present but embedded in the amorphous material. Scale bar, 1 mm. (C–F) Correlation between middle ear defects and hearing sensitivity change with time. (C) Normal ABR thresholds and middle ear structure in a wild type mouse: normal middle ear cavity is full of air, tympanic membrane is transparent and normal morphology of ossicles. (D) Progressively elevated ABR thresholds with age in a Mcph1^tm1a ^/tm1a mouse. Amorphous mass filled the middle ear cavity and outgrew into external ear canal. Ossicles were embedded in the amorphous mass and appeared to have thinner bony structure. (E) Fluctuating ABR thresholds in a Mcph1^tm1a ^/tm1a mouse. Watery effusion with bubbles was seen in the middle ear cavity and normal gross morphology of ossicles. (F) Stable and moderate hearing impairment in a Mcph1^tm1a ^/tm1a mouse. The middle cavity was filled with pus-like secretion. Normal gross morphology of ossicles but with rough surface. Scale bar, 1 mm.