Substrate properties of zebrafish Rtn4b/Nogo and axon regeneration in the zebrafish optic nerve
Substrate properties of zebrafish Rtn4b/Nogo and axon regeneration in the zebrafish optic nerve
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DOI：
10.1002/cne.24253
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发表时间：
2017-10-01
影响因子：
2.5
通讯作者：
Stuermer, Claudia A. O.
中科院分区：
文献类型：
--
作者：
Bodrikov, Vsevolod;Welte, Cornelia;Stuermer, Claudia A. O.
这项研究探讨了为什么受损的视网膜神经节细胞（RGC）轴突在斑马鱼视神经中成功再生，尽管存在大鼠神经突生长抑制剂RTN 4-A/Nogo-A的同系物Rtn 4 b。大鼠Nogo-A和斑马鱼Rtn 4 b在Nogo-A特异性区域中具有特征性基序（M1-4），该区域包含大鼠Nogo-A的最具抑制性的区域delta 20。为了确定斑马鱼M1-4是否与大鼠M1-4和Nogo-A delta 20一样具有抑制性，重组表达蛋白质并用作斑马鱼单细胞RGCs、小鼠海马神经元和金鱼、斑马鱼和鸡视网膜外植体的底物。当提供的同质基板，海马神经元和斑马鱼单细胞RGCs的神经突被抑制斑马鱼M1-4，大鼠M1-4，和Nogo-A delta 20。神经突长度增加时，斑马鱼单细胞RGCs与受体类型特异性拮抗剂，并分别与吗啉代（MO）对S1 PR 2和S1 PR 5a代表候选斑马鱼Nogo-A受体。然而，在条纹试验中，其中M1-4泳道与仅多聚赖氨酸（Plys）泳道交替，来自金鱼、斑马鱼和鸡视网膜外植体的RGC轴突避开大鼠M1-4，但自由穿过斑马鱼M1-4泳道，表明斑马鱼M1-4比大鼠M1-4具有生长许可性和较低的抑制性。视神经和髓鞘的免疫组化染色和斑点杂交显示，在损伤后3-5天轴突再生时，Rtn 4 b在组织和髓鞘中的表达很低。因此，Rtn 4 b似乎不代表轴突在体内再生的主要障碍，因为它对来自视网膜外植体的RGC轴突的抑制较小，并且因为它的低丰度。
This study explored why lesioned retinal ganglion cell (RGC) axons regenerate successfully in the zebrafish optic nerve despite the presence of Rtn4b, the homologue of the rat neurite growth inhibitor RTN4-A/Nogo-A. Rat Nogo-A and zebrafish Rtn4b possess characteristic motifs (M1-4) in the Nogo-A-specific region, which contains delta20, the most inhibitory region of rat Nogo-A. To determine whether zebrafish M1-4 is inhibitory as rat M1-4 and Nogo-A delta20, proteins were recombinantly expressed and used as substrates for zebrafish single cell RGCs, mouse hippocampal neurons and goldfish, zebrafish and chick retinal explants. When offered as homogenous substrates, neurites of hippocampal neurons and of zebrafish single cell RGCs were inhibited by zebrafish M1-4, rat M1-4, and Nogo-A delta20. Neurite length increased when zebrafish single cell RGCs were treated with receptor-type-specific antagonists and, respectively, with morpholinos (MO) against S1PR2 and S1PR5awhich represent candidate zebrafish Nogo-A receptors. In a stripe assay, however, where M1-4 lanes alternate with polylysine-(Plys)-only lanes, RGC axons from goldfish, zebrafish, and chick retinal explants avoided rat M1-4 but freely crossed zebrafish M1-4 lanessuggesting that zebrafish M1-4 is growth permissive and less inhibitory than rat M1-4. Moreover, immunostainings and dot blots of optic nerve and myelin showed that expression of Rtn4b is very low in tissue and myelin at 3-5 days after lesion when axons regenerate. Thus, Rtn4b seems to represent no major obstacle for axon regeneration in vivo because it is less inhibitory for RGC axons from retina explants, and because of its low abundance.