During embryonic development of bilaterally symmetrical organisms, neurons send axons across the midline at specific points to connect the two halves of the nervous system with a commissure. Little is known about the cells at the midline that facilitate this tightly regulated process. We exploit the conserved process of vertebrate embryonic development in the zebrafish model system to elucidate the identity of cells at the midline that may facilitate postoptic (POC) and anterior commissure (AC) development. We have discovered that three different gfap+ astroglial cell morphologies persist in contact with pathfinding axons throughout commissure formation. Similarly, olig2+ progenitor cells occupy delineated portions of the postoptic and anterior commissures where they act as multipotent, neural progenitors. Moreover, we conclude that both gfap+ and olig2+ progenitor cells give rise to neuronal populations in both the telencephalon and diencephalon; however, these varied cell populations showed significant developmental timing differences between the telencephalon and diencephalon. Lastly, we also showed that fli1a+ mesenchymal cells migrate along the presumptive commissure regions before and during midline axon crossing. Furthermore, following commissure maturation, specific blood vessels formed at the midline of the POC and immediately ventral and parallel to the AC. This comprehensive account of the cellular populations that correlate with the timing and position of commissural axon pathfinding has supported the conceptual modeling and identification of the early forebrain architecture that may be necessary for proper commissure development.

中文翻译：

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表征与斑马鱼前脑发育连合相关的不同细胞

在双侧对称生物的胚胎发育过程中，神经元在特定点将轴突穿过中线，以将神经系统的两半与连合连接起来。关于促进这一严格调节过程的中线细胞知之甚少。我们利用斑马鱼模型系统中脊椎动物胚胎发育的保守过程来阐明可能促进视后 (POC) 和前连合 (AC) 发育的中线细胞的身份。我们发现三种不同的gfap + 星形胶质细胞形态在整个连合形成过程中持续与寻路轴突接触。同样，olig2+ 祖细胞占据视后和前连合的划定部分，在那里它们充当多能神经祖细胞。此外，我们得出结论，gfap + 和olig2 + 祖细胞都会在端脑和间脑中产生神经元群。然而，这些不同的细胞群在端脑和间脑之间显示出显着的发育时间差异。最后，我们还展示了fli1a+ 间充质细胞在中线轴突穿越之前和期间沿着假定的连合区域迁移。此外，在连合成熟后，特定血管在 POC 的中线形成，并立即腹侧并平行于 AC。这种对与连合轴突寻路的时间和位置相关的细胞群的全面描述支持了早期前脑结构的概念建模和识别，这可能是适当的连合发育所必需的。