Expression patterns of Eph genes in the “dual visual development” of the lamprey and their significance in the evolution of vision in vertebrates
Expression patterns of Eph genes in the “dual visual development” of the lamprey and their significance in the evolution of vision in vertebrates
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七鳃鳗“双重视觉发育”中Eph基因的表达模式及其在脊椎动物视觉进化中的意义
DOI：
10.1111/ede.12119
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发表时间：
2015
影响因子：
2.9
通讯作者：
Hiroshi Wada
中科院分区：
文献类型：
--
作者：
Daichi G. Suzuki;Yasunori Murakami;Yuji Yamazaki;Hiroshi Wada
图像形成视觉对于动物识别环境中的物体至关重要。在脊椎动物中，这种类型的视觉是通过成对的相机眼睛和视神经的地形投影来实现的。拓扑投影通过轴突引导分子（诸如Eph）的正交梯度来建立。为了探索脊椎动物的图像形成视觉的进化，七鳃鳗属于脊椎动物的基础谱系，是关键动物，因为它们表现出独特的“双重视觉发展”。在胚胎和前砂腔幼体阶段（“初级”阶段），感光的“单眼样”眼睛发育，但没有视网膜顶盖视神经投射。在沙殖幼体晚期（“次级”阶段），眼睛生长并形成照相机眼睛，并且新形成视网膜顶盖突起。变态后，这在成年七鳃鳗视网膜顶盖投影地形，类似于颚口类。在这项研究中，我们探讨了参与Ephsin七鳃鳗“双重视觉发展”和建立的图像形式的视觉。我们发现，在“第二”阶段，在视网膜中存在颌口样正交梯度表达;即，EphB沿背腹轴呈沿着梯度表达，EphC沿前后轴呈沿着梯度表达。然而，在“初级”阶段没有观察到正交梯度表达。这些观察结果表明，Eph可能重新招募的地形“第二”视神经投射的指导。七鳃鳗“双重视觉发育”期间的转变可能代表从原脊索动物样祖先到颌口类脊椎动物祖先的“重演”。
Image‐forming vision is crucial to animals for recognizing objects in their environment. In vertebrates, this type of vision is achieved with paired camera eyes and topographic projection of the optic nerve. Topographic projection is established by an orthogonal gradient of axon guidance molecules, such as Ephs. To explore the evolution of image‐forming vision in vertebrates, lampreys, which belong to the basal lineage of vertebrates, are key animals because they show unique “dual visual development.” In the embryonic and pre‐ammocoete larval stage (the “primary” phase), photoreceptive “ocellus‐like” eyes develop, but there is no retinotectal optic nerve projection. In the late ammocoete larval stage (the “secondary” phase), the eyes grow and form into camera eyes, and retinotectal projection is newly formed. After metamorphosis, this retinotectal projection in adult lampreys is topographic, similar to that of gnathostomes. In this study, we explored the involvement ofEphsin lamprey “dual visual development” and establishment of the image‐form vision. We found that gnathostome‐like orthogonal gradient expression was present in the retina during the “secondary” phase; i.e.,EphBshowed a gradient of expression along the dorsoventral axis, whileEphCwas expressed along the anteroposterior axis. However, no orthogonal gradient expression was observed during the “primary” phase. These observations suggest thatEphsare likely recruited de novo for the guidance of topographical “second” optic nerve projection. Transformations during lamprey “dual visual development” may represent “recapitulation” from a protochordate‐like ancestor to a gnathostome‐like vertebrate ancestor.