A Short Splice Form of Xin-Actin Binding Repeat Containing 2 (XIRP2) Lacking the Xin Repeats Is Required for Maintenance of Stereocilia Morphology and Hearing Function
A Short Splice Form of Xin-Actin Binding Repeat Containing 2 (XIRP2) Lacking the Xin Repeats Is Required for Maintenance of Stereocilia Morphology and Hearing Function
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DOI：
10.1523/jneurosci.3449-14.2015
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发表时间：
2015-02-04
影响因子：
5.3
通讯作者：
Shin, Jung-Bum
中科院分区：
文献类型：
--
作者：
Francis, Shimon P.;Krey, Jocelyn F.;Shin, Jung-Bum
大约三分之一的耳聋基因编码位于毛束的蛋白质，毛束是感觉毛细胞的机械感受细胞器。在之前的研究中，我们使用质谱法来表征头发束的蛋白质组，从而发现了新的束蛋白。其中一种蛋白是Xin-actin binding repeat containing 2 (XIRP2)，这是一种肌动蛋白交联蛋白，先前报道在横纹肌中特异性表达。由于其他肌动蛋白交联体的突变会导致听力损失，因此我们研究了XIRP2在听力功能中的作用。在内耳中，XIRP2在毛细胞中特异性表达，与肌动蛋白束、下表皮板和周向肌动蛋白带中富含肌动蛋白的结构共定位。肽质谱分析显示，该束含有以前未被表征的XIRP2剪接变体，这表明XIRP2在毛细胞中的作用与在肌细胞中的作用有很大不同。为了确定XIRP2在听力中的作用，我们采用聚类规则间隔短回文重复(CRISPR)/ cas9介导的基因组编辑技术诱导小鼠XIRP2基因靶向突变，从而消除内耳XIRP2蛋白的表达。xirp2缺失小鼠的听力功能分析显示高频听力丧失，毛细胞的超微结构扫描电镜分析显示这些小鼠的立体纤毛变性。因此，我们得出结论，XIRP2是毛细胞立体纤毛长期维持所必需的，其功能障碍导致小鼠听力损失。
Approximately one-third of known deafness genes encode proteins located in the hair bundle, the sensory hair cell's mechanoreceptive organelle. In previous studies, we used mass spectrometry to characterize the hair bundle's proteome, resulting in the discovery of novel bundle proteins. One such protein is Xin-actin binding repeat containing 2 (XIRP2), an actin-cross-linking protein previously reported to be specifically expressed in striated muscle. Because mutations in other actin-cross-linkers result in hearing loss, we investigated the role of XIRP2 in hearing function. In the inner ear, XIRP2 is specifically expressed in hair cells, colocalizing with actin-rich structures in bundles, the underlying cuticular plate, and the circumferential actin belt. Analysis using peptide mass spectrometry revealed that the bundle harbors a previously uncharacterized XIRP2 splice variant, suggesting XIRP2's role in the hair cell differs significantly from that reported in myocytes. To determine the role of XIRP2 in hearing, we applied clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated genome-editing technology to induce targeted mutations into the mouse Xirp2 gene, resulting in the elimination of XIRP2 protein expression in the inner ear. Functional analysis of hearing in the resulting Xirp2-null mice revealed high-frequency hearing loss, and ultrastructural scanning electron microscopy analyses of hair cells demonstrated stereocilia degeneration in these mice. We thus conclude that XIRP2 is required for long-term maintenance of hair cell stereocilia, and that its dysfunction causes hearing loss in the mouse.