Otolaryngology Head and Neck Surgery, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, Ohio, United States of America.
PLoS One. 2011 Apr 21;6(4):e19183. doi: 10.1371/journal.pone.0019183.
Immunocytochemical studies have shown that protocadherin-15 (PCDH15) and cadherin-23 (CDH23) are associated with tip links, structures thought to gate the mechanotransducer channels of hair cells in the sensory epithelia of the inner ear. The present report describes functional and structural analyses of hair cells from Pcdh15(av3J) (av3J), Pcdh15(av6J) (av6J) and Cdh23(v2J) (v2J) mice. The av3J and v2J mice carry point mutations that are predicted to introduce premature stop codons in the transcripts for Pcdh15 and Cdh23, respectively, and av6J mice have an in-frame deletion predicted to remove most of the 9th cadherin ectodomain from PCDH15. Severe disruption of hair-bundle morphology is observed throughout the early-postnatal cochlea in av3J/av3J and v2J/v2J mice. In contrast, only mild-to-moderate bundle disruption is evident in the av6J/av6J mice. Hair cells from av3J/av3J mice are unaffected by aminoglycosides and fail to load with [(3)H]-gentamicin or FM1-43, compounds that permeate the hair cell's mechanotransducer channels. In contrast, hair cells from av6J/av6J mice load with both FM1-43 and [(3)H]-gentamicin, and are aminoglycoside sensitive. Transducer currents can be recorded from hair cells of all three mutants but are reduced in amplitude in all mutants and have abnormal directional sensitivity in the av3J/av3J and v2J/v2J mutants. Scanning electron microscopy of early postnatal cochlear hair cells reveals tip-link like links in av6J/av6J mice, substantially reduced numbers of links in the av3J/av3J mice and virtually none in the v2J/v2J mice. Analysis of mature vestibular hair bundles reveals an absence of tip links in the av3J/av3J and v2J/v2J mice and a reduction in av6J/av6J mice. These results therefore provide genetic evidence consistent with PCDH15 and CDH23 being part of the tip-link complex and necessary for normal mechanotransduction.
免疫细胞化学研究表明原钙黏蛋白 15（PCDH15）和钙黏蛋白 23（CDH23）与纤毛尖端相连，这些结构被认为是内耳感觉上皮毛细胞机械转导通道的门控。本报告描述了 Pcdh15（av3J）（av3J）、Pcdh15（av6J）（av6J）和 Cdh23（v2J）（v2J）小鼠的毛细胞的功能和结构分析。av3J 和 v2J 小鼠携带点突变，预计分别在 Pcdh15 和 Cdh23 的转录本中引入过早终止密码子，而 av6J 小鼠具有框内缺失，预计从 PCDH15 中去除大部分第 9 个钙黏蛋白外显子。在 av3J/av3J 和 v2J/v2J 小鼠的整个早期出生后耳蜗中，毛束形态严重破坏。相比之下，av6J/av6J 小鼠中只有轻度至中度束状破坏。av3J/av3J 小鼠的毛细胞不受氨基糖苷类药物的影响，并且不能加载 [(3)H]-庆大霉素或 FM1-43，这两种化合物都可以渗透毛细胞的机械转导通道。相反，av6J/av6J 小鼠的毛细胞可以加载 FM1-43 和 [(3)H]-庆大霉素，并且对氨基糖苷类敏感。可以从所有三种突变体的毛细胞中记录到转导电流，但在所有突变体中幅度降低，并且在 av3J/av3J 和 v2J/v2J 突变体中具有异常的方向敏感性。早期出生后耳蜗毛细胞的扫描电子显微镜显示 av6J/av6J 小鼠中有尖端连接样连接，av3J/av3J 小鼠中的连接数量明显减少，而 v2J/v2J 小鼠中几乎没有。分析成熟的前庭毛束显示 av3J/av3J 和 v2J/v2J 小鼠中没有尖端连接，av6J/av6J 小鼠中连接减少。因此，这些结果提供了遗传证据，表明 PCDH15 和 CDH23 是尖端连接复合物的一部分，是正常机械转导所必需的。
