Development of utricular otoliths, but not saccular otoliths, is necessary for vestibular function and survival in zebrafish.
Development of utricular otoliths, but not saccular otoliths, is necessary for vestibular function and survival in zebrafish.
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DOI：
10.1002/1097-4695(20000615)43:4
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发表时间：
2000-06
期刊：
影响因子：
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通讯作者：
B. Riley;S. Moorman
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文献类型：
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作者：
B. Riley;S. Moorman
我们一直在研究斑马鱼巨石（mnl）突变引起的胚胎前庭功能障碍的后果。 mnl 是一种显性突变，特异性抑制椭圆囊耳石的形成。然而，将mnl/mnl胚胎短暂固定在琼脂糖中，耳囊以某些角度定向，选择性地诱导或防止椭圆形和/或囊状耳石的形成。通过这种非侵入性技术，我们生成了六种表型类别的 mnl/mnl 突变体，分别命名为 S-S、U-U、U-S、S-US、U-US 和 US-US，具体取决于每侧存在的耳石（U，椭圆形耳石；S，囊状耳石）。所有 mnl/mnl 幼虫均在发育第 10 天存活。此后，S-S幼虫的数量迅速减少，可能是因为饥饿，没有一个能存活到成年。所有其他类别的 mnl/mnl 幼虫（至少有一个椭圆囊耳石的幼虫）的存活率接近正常。椭圆囊耳石的存在与否也与早期幼虫发育过程中的前庭功能相关，这通过三个标准来衡量：首先，与野生型幼虫不同，S-S突变幼虫在尾巴向上或尾巴向下倾斜时几乎没有显示出可检测到的眼睛反向旋转。其次，95% 的 S-S 突变幼虫从未获得保持平衡的背朝上姿势的能力。第三，虽然大多数野生型幼虫通过直线游动来响应温和的刺激，但 S-S 幼虫通过快速圆圈游动来响应，表现出突然和频繁的方向变化（“之字形”）和/或滚动和螺旋。 mnl/mnl 幼虫的所有其他表型类别在这些测定中表现正常。这些数据表明，双侧椭圆囊耳石的丧失会破坏感知重力的能力，严重损害平衡和运动协调性，并且总是致命的。至少一只内耳中存在椭圆形耳石对于前庭功能和生存来说是必要且充分的。相比之下，囊状耳石对于这些功能来说是可有可无的。
We have been studying the consequences of embryonic vestibular dysfunction caused by the monolith (mnl) mutation in zebrafish. mnl is a dominant mutation that specifically inhibits formation of utricular otoliths. However, briefly immobilizing mnl/mnl embryos in agarose with the otic vesicle orientated at certain angles selectively induces or prevents formation of utricular and/or saccular otoliths. With this noninvasive technique, we generated six phenotypic classes of mnl/mnl mutants, designated S-S, U-U, U-S, S-US, U-US, and US-US, depending on which otoliths are present on each side (U, utricular otolith; S, saccular otolith). All mnl/mnl larvae survived through day 10 of development. Thereafter, S-S larvae showed a rapid decline, probably because of starvation, and none survived to adulthood. Survival rates in all other classes of mnl/mnl larvae (those having at least one utricular otolith) were close to normal. The presence or absence of utricular otoliths also correlated with vestibular function during early larval development, as measured by three criteria: First, unlike wild-type larvae, S-S mutant larvae showed almost no detectable counter-rotation of the eyes when tilted tail up or tail down. Second, 95% of S-S mutant larvae never acquired the ability to maintain a balanced dorsal-up posture. Third, although most wild-type larvae responded to gentle prodding by swimming in a straight line, S-S larvae responded by swimming in rapid circles, showing sudden and frequent changes in direction ("zigzagging"), and/or rolling and spiraling. All other phenotypic classes of mnl/mnl larvae behaved normally in these assays. These data demonstrate that bilateral loss of utricular otoliths disrupts the ability to sense gravity, severely impairs balance and motor coordination, and is invariably lethal. The presence of a utricular otolith in at least one inner ear is necessary and sufficient for vestibular function and survival. In contrast, saccular otoliths are dispensable for these functions.