The cerebrospinal fluid (CSF) contains an extracellular thread that is conserved in vertebrates and referred to as the Reissner fiber. Genetic ablation in the zebrafish revealed that the Reissner fiber controls body axis morphogenesis in the embryo. Yet, the signaling cascade originating from this fiber to ensure body axis straightening is not fully understood. Here, we explore the functional link between the Reissner fiber and undifferentiated spinal neurons contacting the CSF (CSF-cNs). First, we show that the Reissner fiber is required for the expression of urp2, a neuropeptide expressed in CSF-cNs. Using in vivo calcium imaging, we show that the Reissner fiber is also required for embryonic calcium transients in these spinal neurons. Finally, we study how local adrenergic activation directly in the CSF can substitute for the Reissner fiber-signaling pathway to CSF-cNs and rescue body axis morphogenesis. Our results suggest that the Reissner fiber acts on CSF-cNs to establish body axis morphogensis by controlling the availability of a chemical signal in the CSF.

中文翻译：

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肾上腺素激活可在发育过程中调节从Reissner纤维到脑脊液接触神经元的信号

脑脊液（CSF）包含在脊椎动物中保守的细胞外线，被称为Reissner纤维。斑马鱼的遗传消融表明，赖斯纳纤维控制着胚胎的体轴形态发生。然而，尚未完全了解源自该光纤以确保身体轴伸直的信号级联。在这里，我们探索Reissner纤维和接触CSF（CSF-cNs）的未分化脊髓神经元之间的功能联系。首先，我们证明Reissner纤维是urp2（在CSF-cNs中表达的一种神经肽）的表达所必需的。使用体内钙成像，我们显示，这些脊髓神经元中的胚胎钙瞬变也需要Reissner纤维。最后，我们研究了直接在脑脊液中激活肾上腺素能如何替代Reissner纤维向CSF-cNs的信号通路并拯救体轴形态。我们的结果表明，赖斯纳纤维通过控制CSF中化学信号的可用性，作用于CSF-cNs以建立体轴形态发生。