Roles of the espin actin-bundling proteins in the morphogenesis and stabilization of hair cell stereocilia revealed in CBA/CaJ congenic jerker mice.
Roles of the espin actin-bundling proteins in the morphogenesis and stabilization of hair cell stereocilia revealed in CBA/CaJ congenic jerker mice.
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DOI：
10.1371/journal.pgen.1002032
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发表时间：
2011-03
期刊：
影响因子：
4.5
通讯作者：
Bartles JR
中科院分区：
文献类型：
--
作者：
Sekerková G;Richter CP;Bartles JR
听觉和前庭功能依赖于毛细胞静纤毛的机械感觉阶梯集合，其由微绒毛样前体产生，因为它们的平行肌动蛋白束支架直径增加并且伸长或缩短。毛细胞静纤毛含有多类肌动蛋白捆绑蛋白，但很少有人知道每一类的贡献。为了研究肌动蛋白捆绑蛋白的espin类的作用，我们使用了一种遗传方法，该方法受益于明智的选择小鼠背景品系和杂合性的影响的检查。通过重复回交到近交CBA/CaJ品系中来制备同类jerker小鼠系，所述近交CBA/CaJ品系以优异的听力和最小的年龄相关性听力损失而闻名。我们比较了静纤毛野生型CBA/CaJ小鼠，jerker纯合子，缺乏espin蛋白，由于在espin基因的移码突变，jerker杂合子，含有减少espin水平。espins的缺乏从根本上损害了静纤毛的形态发生，导致静纤毛异常薄而短，差异伸长减少，形成楼梯。静纤毛的平均直径增加不超过0.10-0.14 μm，使静纤毛比野生型细30%-60%，表明它们含有的肌动蛋白丝减少了50%-85%。这些特征表明，在定纤毛平行肌动蛋白束的并置生长和差异伸长中需要espins，并且符合espins在体外和转染细胞中的已知生物活性。jerker杂合子的静纤毛表现出短暂的近端-远端逐渐变细，提示单倍性不足和形态发生减慢，揭示了以前未被识别的组装步骤和中间体。espins的缺乏也导致静纤毛的区域依赖性变性，包括缩短和塌陷。我们的结论是espin肌动蛋白捆绑蛋白的组装和稳定的立纤毛平行肌动蛋白束。静纤毛是内耳毛细胞的指状突起，用于检测声音和运动。静纤毛生长到特定的长度和直径，并形成阶梯状阵列。大小的变化似乎是由一个基本的分子支架的尺寸匹配改变驱动的，该分子支架由一束由肌动蛋白集束蛋白交联的肌动蛋白丝组成。为了阐明espin肌动蛋白捆绑蛋白在毛细胞静纤毛中的作用，我们对jerker突变小鼠的静纤毛大小和形状进行了深入的研究，该小鼠由于espin基因突变而缺乏espin蛋白。我们研究了一种新的和改进的jerker小鼠，其遗传背景以高质量的终身听力而闻名。我们发现，在没有espins，静纤毛不增加直径或完成其伸长，而是弯曲，缩短和消失。虽然具体情况因内耳区域而异，但静纤毛缺陷是深刻的，可以很容易地解释jerker小鼠和具有某些espin基因突变的人类的耳聋和平衡问题。即使将espin水平降低一半，也会导致静纤毛直径的暂时性缺陷。因此，espins在毛细胞静纤毛的形成和维持中起着至关重要的作用。
Hearing and vestibular function depend on mechanosensory staircase collections of hair cell stereocilia, which are produced from microvillus-like precursors as their parallel actin bundle scaffolds increase in diameter and elongate or shorten. Hair cell stereocilia contain multiple classes of actin-bundling protein, but little is known about what each class contributes. To investigate the roles of the espin class of actin-bundling protein, we used a genetic approach that benefited from a judicious selection of mouse background strain and an examination of the effects of heterozygosity. A congenic jerker mouse line was prepared by repeated backcrossing into the inbred CBA/CaJ strain, which is known for excellent hearing and minimal age-related hearing loss. We compared stereocilia in wild-type CBA/CaJ mice, jerker homozygotes that lack espin proteins owing to a frameshift mutation in the espin gene, and jerker heterozygotes that contain reduced espin levels. The lack of espins radically impaired stereociliary morphogenesis, resulting in stereocilia that were abnormally thin and short, with reduced differential elongation to form a staircase. Mean stereociliary diameter did not increase beyond ∼0.10–0.14 µm, making stereocilia ∼30%–60% thinner than wild type and suggesting that they contained ∼50%–85% fewer actin filaments. These characteristics indicate a requirement for espins in the appositional growth and differential elongation of the stereociliary parallel actin bundle and fit the known biological activities of espins in vitro and in transfected cells. The stereocilia of jerker heterozygotes showed a transient proximal-distal tapering suggestive of haploinsufficiency and a slowing of morphogenesis that revealed previously unrecognized assembly steps and intermediates. The lack of espins also led to a region-dependent degeneration of stereocilia involving shortening and collapse. We conclude that the espin actin-bundling proteins are required for the assembly and stabilization of the stereociliary parallel actin bundle. Stereocilia are the fingerlike projections of inner ear hair cells that detect sound and motion. Stereocilia grow to specific lengths and diameters and form staircase-like arrays. The changes in size appear to be driven by matching alterations in the dimensions of an underlying molecular scaffold consisting of a bundle of actin filaments cross-linked by actin-bundling proteins. To elucidate the roles of the espin actin-bundling proteins in hair cell stereocilia, we carry out an in-depth accounting of stereociliary size and shape in the jerker mutant mouse, which lacks the espin proteins because of a mutation in the espin gene. We examine a new and improved jerker mouse with a genetic background known for high-quality lifelong hearing. We find that, in the absence of espins, stereocilia do not increase in diameter or complete their elongation, but instead bend, shorten, and disappear. Although the specifics vary according to inner ear region, the stereociliary defects are profound and can readily account for the deafness and balance problems of jerker mice and humans with certain espin gene mutations. Even reducing espin levels by one-half leads to temporary defects in stereociliary diameter. Thus, espins play crucial roles in the formation and maintenance of hair cell stereocilia.
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影响因子：
2.5
作者：
Lelli, Andrea;Asai, Yukako;Geleoc, Gwenaeelle S. G.
通讯作者：
Geleoc, Gwenaeelle S. G.
影响因子：
7.8
作者：
Bartles, J R;Zheng, L;Li, A;Wierda, A;Chen, B
通讯作者：
Chen, B
影响因子：
5.3
作者：
Furness, David N.;Mahendrasingam, Shanthini;Hackney, Carole M.
通讯作者：
Hackney, Carole M.
DOI：
10.1073/pnas.0900221106
发表时间：
2009-06-16
影响因子：
11.1
作者：
Belyantseva, Inna A.;Perrin, Benjamin J.;Ervasti, James M.
通讯作者：
Ervasti, James M.
影响因子：
2.5
作者：
Li, HW;Liu, H;Heller, S
通讯作者：
Heller, S