Olt Jennifer, Johnson Stuart L, Marcotti Walter
Department of Biomedical Science, University of Sheffield, Sheffield, UK.
Department of Biomedical Science, University of Sheffield, Sheffield, UK
J Physiol. 2014 May 15;592(10):2041-58. doi: 10.1113/jphysiol.2013.265108. Epub 2014 Feb 24.
Hair cells detect and process sound and movement information, and transmit this with remarkable precision and efficiency to afferent neurons via specialized ribbon synapses. The zebrafish is emerging as a powerful model for genetic analysis of hair cell development and function both in vitro and in vivo. However, the full exploitation of the zebrafish is currently limited by the difficulty in obtaining systematic electrophysiological recordings from hair cells under physiological recording conditions. Thus, the biophysical properties of developing and adult zebrafish hair cells are largely unknown. We investigated potassium and calcium currents, voltage responses and synaptic activity in hair cells from the lateral line and inner ear in vivo and using near-physiological in vitro recordings. We found that the basolateral current profile of hair cells from the lateral line becomes more segregated with age, and that cells positioned in the centre of the neuromast show more mature characteristics and those towards the edge retain a more immature phenotype. The proportion of mature-like hair cells within a given neuromast increased with zebrafish development. Hair cells from the inner ear showed a developmental change in current profile between the juvenile and adult stages. In lateral line hair cells from juvenile zebrafish, exocytosis also became more efficient and required less calcium for vesicle fusion. In hair cells from mature zebrafish, the biophysical characteristics of ion channels and exocytosis resembled those of hair cells from other lower vertebrates and, to some extent, those in the immature mammalian vestibular and auditory systems. We show that although the zebrafish provides a suitable animal model for studies on hair cell physiology, it is advisable to consider that the age at which the majority of hair cells acquire a mature-type configuration is reached only in the juvenile lateral line and in the inner ear from >2 months after hatching.
毛细胞检测并处理声音和运动信息，并通过特殊的带状突触以极高的精度和效率将这些信息传递给传入神经元。斑马鱼正逐渐成为一种强大的模型，用于在体外和体内对毛细胞发育和功能进行遗传分析。然而，目前斑马鱼的充分利用受到在生理记录条件下从毛细胞获得系统电生理记录的困难的限制。因此，发育中和成年斑马鱼毛细胞的生物物理特性在很大程度上尚不清楚。我们在体内以及使用近生理条件下的体外记录，研究了斑马鱼侧线和内耳毛细胞中的钾电流和钙电流、电压反应以及突触活动。我们发现，侧线毛细胞的基底外侧电流分布随年龄增长变得更加分离，位于神经丘中心的细胞表现出更成熟的特征，而靠近边缘的细胞则保留更不成熟的表型。在给定的神经丘内，类似成熟的毛细胞比例随着斑马鱼的发育而增加。内耳毛细胞在幼年和成年阶段之间电流分布出现发育变化。在幼年斑马鱼的侧线毛细胞中，胞吐作用也变得更有效率，并且囊泡融合所需的钙更少。在成熟斑马鱼的毛细胞中，离子通道和胞吐作用的生物物理特性类似于其他低等脊椎动物的毛细胞，并且在某种程度上类似于未成熟哺乳动物前庭和听觉系统中的毛细胞。我们表明，虽然斑马鱼为毛细胞生理学研究提供了合适的动物模型，但建议考虑到大多数毛细胞仅在幼年侧线以及孵化后超过2个月的内耳中才达到成熟型配置的年龄。
