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The Journal of Neuroscience, February 15, 2006, 26(7):1991-1999; doi:10.1523/JNEUROSCI.5055-05.2006

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Cellular/Molecular
Connexin29 Is Highly Expressed in Cochlear Schwann Cells, and It Is Required for the Normal Development and Function of the Auditory Nerve of Mice

Wenxue Tang,¹ Yanping Zhang,¹ Qing Chang,¹ Shoab Ahmad,¹ Ian Dahlke,¹ Hong Yi,³ Ping Chen,^1,2 David L. Paul,⁴ and Xi Lin^1,2

¹Departments of Otolaryngology, ²Cell Biology, and ³Electron Microscope Core Laboratory, Emory University School of Medicine, Atlanta, Georgia 30322, and ⁴Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115

Correspondence should be addressed to Dr. Xi Lin, Departments of Otolaryngology and Cell Biology, Emory University School of Medicine, Atlanta, GA 30322. Email: xlin2{at}emory.edu

Connexins (Cxs) are a family of protein subunits constituting gap junctions, which facilitate exchanges of molecules important for cellular signaling and metabolic activities intercellularly or between different regions of the cytoplasm in the same cells. Mutations in Cxs are the major cause of nonsyndromic childhood deafness, which are mostly found in Cx26 and Cx30 expressed in cochlear supporting cells and fibrocytes. So far, little is known about the functional contribution of Cxs in other types of cochlear cells. Here, we show that Cx29 was highly expressed in the cochlea. The developmental expression time course of Cx29 was similar to that of a myelin marker [myelin associate glycoprotein (MAG)]. Immunolabeling identified Cx29 exclusively in the Schwann cells myelinating the soma and fiber of spiral ganglion (SG) neurons. The absence of the Cx29 gene in mice (Cx29^–/– mice), with a penetrance of 50%, caused a delay in the maturation of hearing thresholds, an early loss of high-frequency sensitivities, a prolongation in latency and distortion in the wave I of the auditory brainstem responses, and elevated sensitivity to noise damages. The morphology of sensory hair cells and otoacoustic emissions that depend on the integrity of hair cells were normal in Cx29^–/– mice. In contrast, decreases in MAG expression and severe demyelination at the soma of SG neurons were found in Cx29^–/– mice. Our findings demonstrated the requirement of Cx29 for normal cochlear functions and suggest that Cx29 is a new candidate gene for studying the auditory neuropathy.

Key words: connexin29; gap junction; myelin; cochlear Schwann cells; spiral ganglion neuron; cochlea

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Received April 26, 2005; revised Jan. 3, 2006; accepted Jan. 4, 2006.

Correspondence should be addressed to Dr. Xi Lin, Departments of Otolaryngology and Cell Biology, Emory University School of Medicine, Atlanta, GA 30322. Email: xlin2{at}emory.edu

This article has been cited by other articles:

				P. Wangemann Supporting sensory transduction: cochlear fluid homeostasis and the endocochlear potential J. Physiol., October 1, 2006; 576(1): 11 - 21. [Abstract] [Full Text] [PDF]

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