The dimensions and composition of stereociliary rootlets in mammalian cochlear hair cells: Comparison between high- and low-frequency cells and evidence for a connection to the lateral membrane
The dimensions and composition of stereociliary rootlets in mammalian cochlear hair cells: Comparison between high- and low-frequency cells and evidence for a connection to the lateral membrane
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DOI：
10.1523/jneurosci.1154-08.2008
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发表时间：
2008-06-18
影响因子：
5.3
通讯作者：
Hackney, Carole M.
中科院分区：
文献类型：
--
作者：
Furness, David N.;Mahendrasingam, Shanthini;Hackney, Carole M.
脊椎动物耳蜗毛细胞的感觉束由含有肌动蛋白的立体纤毛组成，这些纤毛被认为在机械刺激时在脚踝处弯曲。立体纤毛有浓密的细根，通过踝关节区域延伸，将其固定在角质层上。由于该区域可能在长时间高频刺激下对束的刚度和耐久性起重要作用，因此我们使用光学和电子显微镜研究了鼠类耳蜗顶端（低频）和底部（高频）区域的细根相对于立体纤毛的结构和尺寸。采用包埋后免疫金标记法研究原肌球蛋白、谱蛋白、β -肌动蛋白、-肌动蛋白、espin和prestin的组成。小根有一厚的中心核，在踝部加宽，并嵌入在角质层的丝状网中。在一个特定的频率区域内，根茎长度与直立纤毛高度相关，但在不同的区域之间，它的变化不成比例；因此，在等量行中，顶端立体纤毛的高度约为基部立体纤毛的两倍，但根的长度增加得少得多。一些小根接触紧密的连接，下面的束的两端。细根中含有spectrin、原肌球蛋白和-和-actin，但未检测到espin；在根尖膜和连接膜附近也可见到Spectrin，而prestin则局限于连接以下的基底侧膜。这些数据表明，根状物加强踝关节区域以提供耐久性，并可能与侧壁接触，为立体纤毛提供额外的锚定或为束与侧壁之间的相互作用提供途径。
The sensory bundle of vertebrate cochlear hair cells consists of actin-containing stereocilia that are thought to bend at their ankle during mechanical stimulation. Stereocilia have dense rootlets that extend through the ankle region to anchor them into the cuticular plate. Because this region may be important in bundle stiffness and durability during prolonged stimulation at high frequencies, we investigated the structure and dimensions of rootlets relative to the stereocilia in apical (low-frequency) and basal (high-frequency) regions of rodent cochleae using light and electron microscopy. Their composition was investigated using postembedding immunogold labeling of tropomyosin, spectrin, beta-actin, gamma-actin, espin, and prestin. The rootlets have a thick central core that widens at the ankle, and are embedded in a filamentous meshwork in the cuticular plate. Within a particular frequency region, rootlet length correlates with stereociliary height but between regions it changes disproportionately; apical stereocilia are, thus, approximately twice the height of basal stereocilia in equivalent rows, but rootlet lengths increase much less. Some rootlets contact the tight junctions that underlie the ends of the bundle. Rootlets contain spectrin, tropomyosin, and beta- and gamma-actin, but espin was not detected; spectrin is also evident near the apical and junctional membranes, whereas prestin is confined to the basolateral membrane below the junctions. These data suggest that rootlets strengthen the ankle region to provide durability and may contact with the lateral wall either to give additional anchoring of the stereocilia or to provide a route for interactions between the bundle and the lateral wall.