Bolte Petra, Bleibaum Florian, Einwich Angelika, Günther Anja, Liedvogel Miriam, Heyers Dominik, Depping Anne, Wöhlbrand Lars, Rabus Ralf, Janssen-Bienhold Ulrike, Mouritsen Henrik
Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.
Research Centre for Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany.
PLoS One. 2016 Mar 8;11(3):e0147819. doi: 10.1371/journal.pone.0147819. eCollection 2016.
Cryptochromes are ubiquitously expressed in various animal tissues including the retina. Some cryptochromes are involved in regulating circadian activity. Cryptochrome proteins have also been suggested to mediate the primary mechanism in light-dependent magnetic compass orientation in birds. Cryptochrome 1b (Cry1b) exhibits a unique carboxy terminus exclusively found in birds so far, which might be indicative for a specialised function. Cryptochrome 1a (Cry1a) is so far the only cryptochrome protein that has been localised to specific cell types within the retina of migratory birds. Here we show that Cry1b, an alternative splice variant of Cry1a, is also expressed in the retina of migratory birds, but it is primarily located in other cell types than Cry1a. This could suggest different functions for the two splice products. Using diagnostic bird-specific antibodies (that allow for a precise discrimination between both proteins), we show that Cry1b protein is found in the retinae of migratory European robins (Erithacus rubecula), migratory Northern Wheatears (Oenanthe oenanthe) and pigeons (Columba livia). In all three species, retinal Cry1b is localised in cell types which have been discussed as potentially well suited locations for magnetoreception: Cry1b is observed in the cytosol of ganglion cells, displaced ganglion cells, and in photoreceptor inner segments. The cytosolic rather than nucleic location of Cry1b in the retina reported here speaks against a circadian clock regulatory function of Cry1b and it allows for the possible involvement of Cry1b in a radical-pair-based magnetoreception mechanism.
隐花色素在包括视网膜在内的各种动物组织中普遍表达。一些隐花色素参与调节昼夜节律活动。隐花色素蛋白也被认为介导鸟类光依赖磁罗盘定向的主要机制。隐花色素1b（Cry1b）表现出迄今为止仅在鸟类中发现的独特羧基末端，这可能表明其具有特殊功能。隐花色素1a（Cry1a）是迄今为止唯一一种已定位到候鸟视网膜内特定细胞类型的隐花色素蛋白。在这里，我们表明Cry1b是Cry1a的一种可变剪接变体，也在候鸟视网膜中表达，但它主要位于与Cry1a不同的细胞类型中。这可能表明这两种剪接产物具有不同的功能。使用诊断性鸟类特异性抗体（能够精确区分这两种蛋白质），我们发现Cry1b蛋白存在于欧洲知更鸟（欧亚鸲）、白斑黑石鵖和鸽子的视网膜中。在这三个物种中，视网膜Cry1b定位于已被讨论为可能非常适合磁感受的细胞类型中：在神经节细胞、移位神经节细胞的细胞质以及光感受器内段中观察到Cry1b。本文报道的视网膜中Cry1b的细胞质而非细胞核定位表明Cry1b不具有昼夜节律钟调节功能，并且它可能参与基于自由基对的磁感受机制。
