Expression and tyrosine phosphorylation of Eph receptors suggest multiple mechanisms in patterning of the visual system
Expression and tyrosine phosphorylation of Eph receptors suggest multiple mechanisms in patterning of the visual system
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DOI：
10.1006/dbio.1997.8786
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发表时间：
1998-01-01
影响因子：
2.7
通讯作者：
Pasquale, EB
中科院分区：
文献类型：
--
作者：
Connor, RJ;Menzel, P;Pasquale, EB
EphA 3受体酪氨酸激酶已经涉及在视网膜神经节细胞的轴突在视顶盖中延伸时引导它们。涉及视网膜轴突上的EphA 3受体及其配体ephrin-A2和ephrin-A5的相反梯度的排斥机制在顶盖中影响视网膜顶盖投影的地形图绘制。为了研究Eph家族在视觉系统模式中的整体作用，我们使用原位杂交技术在胚胎第8天定位鸡视网膜和视顶盖中的9个Eph受体。所检查的受体中的三种对应于EphA 2、EphA 6和EphA 7的新的鸡同源物。出乎意料的是，我们发现许多Eph受体不仅在视网膜神经节细胞中表达，而且在顶盖细胞中也表达。特别是，EphA 3 mRNA在前顶盖中显著表达，其模式与ephrin-A2和ephrin-A5的模式相反。类似地，肝配蛋白-A5不仅在顶盖细胞中表达，而且在鼻视网膜中表达，其模式与其受体EphA 3的模式相反，并且与其另一种受体EphA 4的模式部分重叠。与视网膜中EphA 4的均匀分布和EphA 4配体的偏振分布一致，用抗磷酸酪氨酸抗体探测来自视网膜不同部分的EphA 4免疫沉淀物揭示了受体磷酸化的空间差异。这些复杂的表达模式和酪氨酸磷酸化表明，Eph受体和肝配蛋白有助于通过多种机制建立视网膜轴突的拓扑结构，除了在视网膜内和顶盖内组织中发挥作用。(C)北京：科学出版社.
The EphA3 receptor tyrosine kinase has been implicated in guiding the axons of retinal ganglion cells as they extend in the optic tectum. A repulsive mechanism involving opposing gradients of the EphA3 receptor on retinal axons and its Ligands, ephrin-A2 and ephrin-A5, in the tectum influences topographic mapping of the retinotectal projection. To investigate the overall role of the Eph family in patterning of the visual system, we have used in situ hybridization to localize nine Eph receptors in the chicken retina and optic tectum at Embryonic Day 8. Three of the receptors examined correspond to the novel chicken homologs of EphA2, EphA6, and EphA7. Unexpectedly, we found that many Eph receptors are expressed not only in retinal ganglion cells, but also in tectal cells. In particular, EphA3 mRNA is prominently expressed in the anterior tectum, with a pattern reciprocal to that of ephrin-A2 and ephrin-A5. Similarly, ephrin-A5 is expressed not only in tectal cells but also in the nasal retina, with a pattern reciprocal to that of its receptor EphA3 and partially overlapping with that of its other receptor EphA4. Consistent with the even distribution of EphA4 and the polarized distribution of EphA4 Ligands in the retina, probing EphA4 immunoprecipitates from different sectors of the retina with anti-phosphotyrosine antibodies revealed spatial differences in receptor phosphorylation. These complex patterns of expression and tyrosine phosphorylation suggest that Eph receptors and ephrins contribute to establishing topography of retinal axons through multiple mechanisms, in addition to playing a role in intraretinal and intratectal organization. (C) 1998 Academic Press.