Webb SW, Grillet N, Andrade LR, et al. Regulation of PCDH15 function in mechanosensory hair cells by alternative splicing of the cytoplasmic domain

Dorris Neuroscience Center and Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Development (Impact Factor: 6.46). 04/2011; 138(8):1607-17. DOI: 10.1242/dev.060061
Source: PubMed

ABSTRACT Protocadherin 15 (PCDH15) is expressed in hair cells of the inner ear and in photoreceptors of the retina. Mutations in PCDH15 cause Usher Syndrome (deaf-blindness) and recessive deafness. In developing hair cells, PCDH15 localizes to extracellular linkages that connect the stereocilia and kinocilium into a bundle and regulate its morphogenesis. In mature hair cells, PCDH15 is a component of tip links, which gate mechanotransduction channels. PCDH15 is expressed in several isoforms differing in their cytoplasmic domains, suggesting that alternative splicing regulates PCDH15 function in hair cells. To test this model, we generated three mouse lines, each of which lacks one out of three prominent PCDH15 isoforms (CD1, CD2 and CD3). Surprisingly, mice lacking PCDH15-CD1 and PCDH15-CD3 form normal hair bundles and tip links and maintain hearing function. Tip links are also present in mice lacking PCDH15-CD2. However, PCDH15-CD2-deficient mice are deaf, lack kinociliary links and have abnormally polarized hair bundles. Planar cell polarity (PCP) proteins are distributed normally in the sensory epithelia of the mutants, suggesting that PCDH15-CD2 acts downstream of PCP components to control polarity. Despite the absence of kinociliary links, vestibular function is surprisingly intact in the PCDH15-CD2 mutants. Our findings reveal an essential role for PCDH15-CD2 in the formation of kinociliary links and hair bundle polarization, and show that several PCDH15 isoforms can function redundantly at tip links.

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Available from: Leonardo Rodrigues Andrade, Sep 29, 2015
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    • "Interestingly, these mice present circular hair bundles with a centered kinocilium, a phenotype similar to that seen in Ift88 KO mutant. Like the Ift88 KO mutant, PCDH15-CD2 deficient mice present a normal distribution of PCP proteins in the sensory epithelia, suggesting that PCDH15-CD2 acts downstream of the PCP signaling pathway (Webb et al., 2011). "
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    ABSTRACT: The inner ear is one of the best systems in mammals to study planar cell polarity (PCP). During development of the inner ear, the PCP pathway controls the convergent extension and polarization of the stereociliary bundles of sensory hair cells of the organ of Corti. These two mechanisms are essential for the integrity of the sensory epithelium and for hearing. The discovery of several mutants, presenting a misorientation of the stereociliary bundles in the inner ear, permitted identification of the core genes that control PCP mechanisms. However, PCP proteins acting downstream in this pathway still remain unclear. Emerging evidences have shown that Usher proteins, which are essential for the establishment of various stereociliary links and mechanotransduction complex, and Bardet-Biedl Syndrome (BBS) proteins, which are involved in ciliogenesis, could be components of the PCP pathway. Regarding these new elements, it appears essential to put PCP proteins in a hearing context.
    Inner Ear Development and Hearing Loss, Edited by Saima Riazuddin, Zubair Ahmed, 01/2013: chapter Usher and Bardet-Biedl syndrome proteins: New pieces in the planar cell polarity puzzle; Nova publishers., ISBN: 978-1-62417-012-6
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    • "Expression vectors for PCDH15-CD3, CDH23, harmonin, and N-cadherin have been described (Franco et al., 2011; Kazmierczak et al., 2007; Siemens et al., 2002; Webb et al., 2011). PCDH15-CR 5 0 GGGCCCCTCGAGATTGCGCTCTCTCCCAGTTCTT 3 0 , containing an Xho I site; 5 0 CCCAAGCTTTAAGTTCCTGGACGGCAAA CTG 3 0 , containing a Hind III site. "
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    ABSTRACT: Hair cells are mechanosensors for the perception of sound, acceleration, and fluid motion. Mechanotransduction channels in hair cells are gated by tip links, which connect the stereocilia of a hair cell in the direction of their mechanical sensitivity. The molecular constituents of the mechanotransduction channels of hair cells are not known. Here, we show that mechanotransduction is impaired in mice lacking the tetraspan TMHS. TMHS binds to the tip-link component PCDH15 and regulates tip-link assembly, a process that is disrupted by deafness-causing Tmhs mutations. TMHS also regulates transducer channel conductance and is required for fast channel adaptation. TMHS therefore resembles other ion channel regulatory subunits such as the transmembrane alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor regulatory proteins (TARPs) of AMPA receptors that facilitate channel transport and regulate the properties of pore-forming channel subunits. We conclude that TMHS is an integral component of the hair cell's mechanotransduction machinery that functionally couples PCDH15 to the transduction channel.
    Cell 12/2012; 151(6):1283-95. DOI:10.1016/j.cell.2012.10.041 · 32.24 Impact Factor
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    • "In zebrafish vestibular hair cells, loss of the kinocilium ultimately results in cell death (Tsujikawa and Malicki, 2004). Interestingly, in mouse auditory cells, specific elimination of kinocilial links also results in degeneration of hair cells (Webb et al., 2011). This degeneration is surprising since mature auditory hair cells do not maintain kinocilia after development. "
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    ABSTRACT: Mechanosensitive cilia are vital to signaling and development across many species. In sensory hair cells, sound and movement are transduced by apical hair bundles. Each bundle is comprised of a single primary cilium (kinocilium) flanked by multiple rows of actin-filled projections (stereocilia). Extracellular tip links that interconnect stereocilia are thought to gate mechanosensitive channels. In contrast to stereocilia, kinocilia are not critical for hair-cell mechanotransduction. However, by sequentially imaging the structure of hair bundles and mechanosensitivity of individual lateral-line hair cells in vivo, we uncovered a central role for kinocilia in mechanosensation during development. Our data demonstrate that nascent hair cells require kinocilia and kinocilial links for mechanosensitivity. Although nascent hair bundles have correct planar polarity, the polarity of their responses to mechanical stimuli is initially reversed. Later in development, a switch to correctly polarized mechanosensitivity coincides with the formation of tip links and the onset of tip-link-dependent mechanotransduction.
    Developmental Cell 08/2012; 23(2):329-41. DOI:10.1016/j.devcel.2012.05.022 · 9.71 Impact Factor
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