Zebrafish Cacna1fa is required for cone photoreceptor function and synaptic ribbon formation
Zebrafish Cacna1fa is required for cone photoreceptor function and synaptic ribbon formation
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DOI：
10.1093/hmg/ddu009
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发表时间：
2014-06-01
影响因子：
3.5
通讯作者：
Taylor, Michael R.
中科院分区：
文献类型：
--
作者：
Jia, Sujuan;Muto, Akira;Taylor, Michael R.
人类CACNA1F基因突变导致不完全先天性静止性夜盲症2型（CSNB2），这是一种非进行性、临床异质性的视网膜疾病。然而，CSNB2的分子机制尚未被充分探索。在这里，我们描述了一个盲斑马鱼突变体的位置克隆，等到黑暗（wud），编码斑马鱼同源的人类CACNA1F。我们鉴定了两种斑马鱼cacna1f相似物，并表明cacna1fa转录本（在wud中突变的基因）仅在感光层表达。我们证明了Cacna1fa定位于光感受器突触，而在wud突变体中不存在。视网膜电图显示，wud突变体的视锥光感受器反应异常，表明突触传递存在缺陷。虽然没有明显的形态学差异，但我们发现wud突变体缺乏突触带，而wud对于突触带的发育至关重要。我们发现，在成年突变体中，最重要的突触带蛋白Ribeye含量较低且定位错误。除了克隆wud外，我们还发现synaptojanin 1 （synj1）是具有浮动突触带的盲突变体slacker （slak）的缺陷基因。我们发现Cacna1fa在slak光感受器中表达，Synj1最初在slak光感受器中表达，但在受精后5 d时缺失。总之，我们的数据表明，Cacna1fa对于锥体光感受器功能和突触带形成至关重要，并揭示了l型电压依赖性钙通道在突触带蛋白的表达和/或分布中先前未知的关键作用，为研究人类CSNB2患者的临床变异性提供了一个新的模型。
Mutations in the human CACNA1F gene cause incomplete congenital stationary night blindness type 2 (CSNB2), a non-progressive, clinically heterogeneous retinal disorder. However, the molecular mechanisms underlying CSNB2 have not been fully explored. Here, we describe the positional cloning of a blind zebrafish mutant, wait until dark (wud), which encodes a zebrafish homolog of human CACNA1F. We identified two zebrafish cacna1f paralogs and showed that the cacna1fa transcript (the gene mutated in wud) is expressed exclusively in the photoreceptor layer. We demonstrated that Cacna1fa localizes at the photoreceptor synapse and is absent from wud mutants. Electroretinograms revealed abnormal cone photoreceptor responses from wud mutants, indicating a defect in synaptic transmission. Although there are no obvious morphological differences, we found that wud mutants lacked synaptic ribbons and that wud is essential for the development of synaptic ribbons. We found that Ribeye, the most prominent synaptic ribbon protein, was less abundant and mislocalized in adult wud mutants. In addition to cloning wud, we identified synaptojanin 1 (synj1) as the defective gene in slacker (slak), a blind mutant with floating synaptic ribbons. We determined that Cacna1fa was expressed in slak photoreceptors and that Synj1 was initially expressed wud photoreceptors, but was absent by 5 days postfertilization. Collectively, our data demonstrate that Cacna1fa is essential for cone photoreceptor function and synaptic ribbon formation and reveal a previously unknown yet critical role of L-type voltage-dependent calcium channels in the expression and/or distribution of synaptic ribbon proteins, providing a new model to study the clinical variability in human CSNB2 patients.