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Ick ciliary kinase is essential for planar cell polarity formation in inner ear hair cells and hearing function.

Research paper by Shio S Okamoto, Taro T Chaya, Yoshihiro Y Omori, Ryusuke R Kuwahara, Shun S Kubo, Hirofumi H Sakaguchi, Takahisa T Furukawa

Indexed on: 25 Jan '17Published on: 25 Jan '17Published in: The Journal of neuroscience : the official journal of the Society for Neuroscience



Abstract

Cellular asymmetries play crucial roles in development and organ function. The planar cell polarity (PCP) signaling pathway is involved in the establishment of cellular asymmetry within the plane of a cell sheet. Inner ear sensory hair cells, which have several rows of staircase-like stereocilia and one kinocilium located at the vertex of the stereocilia protruding from the apical surface of each hair cell, exhibit a typical form of PCP. While connections between cilia and PCP signaling in vertebrate development have been reported, their precise nature is not well understood. In the inner ear development, several ciliary proteins are known to play a role in PCP formation. In the current study, we investigated a functional role for intestinal cell kinase (Ick), which regulates intraflagellar transport (IFT) at the tip of cilia, in the mouse inner ear. A lack of Ick in the developing inner ear resulted in PCP defects in the cochlea, including misorientation or misshaping of stereocilia and aberrant localization of the kinocilium and basal body in the apical and middle turns, leading to auditory dysfunction. We also observed abnormal ciliary localization of Ift88 in both hair cells and supporting cells. Taken together, our results show that Ick ciliary kinase is essential for PCP formation in inner ear hair cells, suggesting that ciliary transport regulation is important for PCP signaling.The cochlea in the inner ear is the hearing organ. Planar cell polarity (PCP) in hair cells in the cochlea is essential for mechanotransduction and refers to the asymmetric structure consisting of stereociliary bundles and the kinocilium on the apical surface of the cell body. We previously reported that a ciliary kinase, Ick, regulates intraflagellar transport (IFT). Here we found that loss of Ick leads to abnormal localization of the IFT component in kinocilia, PCP defects in hair cells, and hearing dysfunction. Our study defines the association of ciliary transport regulation with PCP formation in hair cells and hearing function.