Analysis of zebrafish cryptochrome 2 and 4 expression in UV cone photoreceptors
Analysis of zebrafish cryptochrome 2 and 4 expression in UV cone photoreceptors
复制标题
DOI：
10.1016/j.gep.2020.119100
复制
发表时间：
2020-01-01
影响因子：
1.2
通讯作者：
Waskiewicz, Andrew J.
中科院分区：
文献类型：
--
作者：
Balay, Spencer D.;Widen, Sonya A.;Waskiewicz, Andrew J.
隐花色素（Cry）是一种古老的黄素蛋白，已知可以调节昼夜节律。在植物和一些动物中，Cry 对蓝光敏感，因为它能够结合发色团黄素腺嘌呤二核苷酸 (FAD)。 Cry 也被认为在磁接收中发挥作用，因为它可以与对磁场敏感的 FAD 产生光依赖性自由基对（Ritz2000；Liedvogel 等人，2007；Solov'yov 等人，2014）。哭泣在各种动物的视觉系统中表达，并且与鸟类的短波长和长波长视锥光感受器特异性地共定位（Bischof 等，2011；Gunther 等，2018）。然而，磁感受并不局限于鸟类，其他脊椎动物的光感受器中cry基因的表达情况尚不清楚。在这里，我们使用斑马鱼来检查cry家族基因的视网膜表达模式。斑马鱼有七个cry基因，虽然大多数是已知的生物钟调节基因，但对cry2和cry4的了解相对较少（Haug等人，2015；Liu等人，2015）。因此，我们探索了幼虫和成年斑马鱼视网膜中cry2和cry4的表达。我们证明cry4主要在短波长紫外线（UV）敏感的视锥细胞中表达，而cry2在白天的紫外线视锥细胞和其他视网膜光感受器中表达。使用硝基还原酶（NTZ）介导的细胞消融和qRT-PCR，我们发现当UV锥体被消融时cry4表达显着降低，但当邻近的短波长敏感的蓝色锥体被消融时则不会。紫外线锥体消融后cry2 表达降低，但仍可显着检测到，而蓝锥体消融不会改变cry2 表达。这项研究提供了斑马鱼视网膜中cry2和cry4表达的更详细注释，并强调了一种完善的消融范例来测试鱼的磁感受是否需要光感受器的可行性。尽管成年斑马鱼磁感受的证据在过去十年中已经获得了大量证据（Shcherbakov et al., 2005; Takebe et al., 2012; Krylov et al., 2016; Myklatun et al., 2018），但介导机制仍然未知。此外，尽管有限的证据表明斑马鱼幼鱼具有磁感受能力，但许多其他幼鱼也具有特有的磁感。红鲑鱼苗、珊瑚礁鱼幼体、青鳉幼体和大西洋黑线鳕幼体已被证明对磁场有反应（Quinn；1980；Bottesch 等人，2016；O'Connor 和 Muheim。2017；Myklatun 等人，2018；Cresci 等人，2019）。如果哭声视锥细胞的相互作用在鱼体内是保守的，我们的发现可能暗示了一种潜在的机制，例如紫外线视锥细胞似乎准备通过光感受器亚型特异性的哭声表达来进行光依赖性磁感受。
Cryptochromes (Cry) are ancient flavoproteins known to regulate circadian rhythms. In plants and some animals, Cry is sensitive to blue light due to its ability to bind the chromophore flavin adenine dinucleotide (FAD). Cry is also suggested to function in magnetoreception, since it can create light-dependent radical pairs with FAD that are sensitive to magnetic fields (Ritz2000; Liedvogel et al., 2007; Solov'yov et al., 2014). Cry is expressed in the visual system of various animals and specifically co-localizes with both short- and long-wavelength cone photoreceptors in birds (Bischof et al., 2011; Gunther et al., 2018). However, magnetoreception is not limited to birds and the expression of cry genes in the photoreceptors of other vertebrates is unknown. Here, we use zebrafish to examine the retinal expression pattern of cry family genes. Zebrafish have seven cry genes and while most are known regulators of the circadian clock, relatively little is known about cry2 and cry4 (Haug et al., 2015; Liu et al., 2015). Therefore, we explored cry2 and cry4 expression in the larval and adult zebrafish retina. We demonstrate that cry4 is predominantly expressed in the short-wavelength ultraviolet (UV)-sensitive cone photoreceptors, while cry2 is expressed in UV cones and additional retinal photoreceptors during the day. Using Nitroreductase (NTZ)-mediated cell ablation and qRT-PCR, we find that cry4 expression significantly decreases when UV cones are ablated, but not when the neighboring short-wavelength sensitive blue cones are ablated. cry2 expression decreases after UV cone ablation but is still significantly detectable, while blue cone ablation does not alter cry2 expression. This study provides a more detailed annotation of cry2 and cry4 expression in the zebrafish retina and highlights the feasibility of a well-established ablation paradigm to test if photoreceptors are required for magnetoreception in fish. Although evidence of magnetoreception in adult zebrafish has gained considerable evidence over the last decade (Shcherbakov et al., 2005; Takebe et al., 2012; Krylov et al., 2016; Myklatun et al., 2018) the mediating mechanism(s) remain unknown. Additionally, despite limited evidence that larval zebrafish are magnetoreceptive, many other larval fish have a characterized magnetic sense; sockeye salmon fry, larval coral reef fish, larval medaka and larval Atlantic haddock have been shown to be responsive to magnetic fields (Quinn; 1980; Bottesch et al., 2016; O'Connor and Muheim. 2017; Myklatun et al., 2018; Cresci, et al. 2019). If cry-cone interactions are conserved within fish, our findings may suggest one potential mechanism, such that UV cones appear poised for light-dependent magnetoreception via photoreceptor subtypespecific expression of cry.