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This Article Full Text Full Text (PDF) All Versions of this Article: 100/4/2287    most recent 90707.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nie, L. Articles by Yamoah, E. N. PubMed PubMed Citation Articles by Nie, L. Articles by Yamoah, E. N.

Molecular Identity and Functional Properties of a Novel T-Type Ca²⁺ Channel Cloned From the Sensory Epithelia of the Mouse Inner Ear

¹Center for Neuroscience and ²Program in Communication Science, University of California Davis, Davis, California; ³Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xi'an, China; ⁴Department of Otorhinolaryngology, University of Pennsylvania, Philadelphia, Pennsylvania; ⁵Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida; and ⁶School of Biological Sciences, University of Sussex, Brighton, United Kingdom

Submitted 26 June 2008; accepted in final form 12 August 2008

The molecular identity of non-Ca_v1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca²⁺-dependent functions is indisputable. Recently, a transient Ca_v3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in the chicken basilar papilla. The Ca_v3.1 current promotes spontaneous activity of the developing hair cell, which may be essential for synapse formation. Here, we have isolated and sequenced the full-length complementary DNA of a distinct isoform of Ca_v3.1 in the mouse inner ear. The channel is derived from alternative splicing of exon14, exon25A, exon34, and exon35. Functional expression of the channel in Xenopus oocytes yielded Ca²⁺ currents, which have a permeation phenotype consistent with T-type channels. However, unlike most multiion channels, the T-type channel does not exhibit the anomalous mole fraction effect, possibly reflecting comparable permeation properties of divalent cations. The Ca_v3.1 channel was expressed in sensory and nonsensory epithelia of the inner ear. Moreover, there are profound changes in the expression levels during development. The differential expression of the channel during development and the pharmacology of the inner ear Ca_v3.1 channel may have contributed to the difficulties associated with identification of the non-Ca_v1.3 currents.