Earliest craniates possess a newly enlarged, elaborated forebrain with new cell types and neuronal networks. A key question in vertebrate evolution is when and how this cerebral expansion took place. The exon-junction complex (EJC) plays an essential role in mRNA processing of all Eukarya. Recently, it has been proposed that the EJC represses recursive RNA splicing in Deuterostomes, with implication in human brain diseases like microcephaly and depression. However, the EJC or EJC subunit contribution to brain development in non-vertebrate Deuterostomes remained unknown. Being interested in the evolution of chordate characters, we focused on the model species, Branchiostoma lanceolatum (Cephalochordata) and Ciona robusta (Tunicata), with the aim to investigate the ancestral and the derived expression state of Magoh orthologous genes. This study identifies that Magoh is part of a conserved syntenic group exclusively in vertebrates and suggests that Magoh has experienced duplication and loss events in mammals. During early development in amphioxus and ascidian, maternal contribution and zygotic expression of Magoh genes in various types of progenitor cells and tissues are consistent with the condition observed in other Bilateria. Later in development, we also show expression of Magoh in the brain of cephalochordate and ascidian larvae. Collectively, these results provide a basis to further define what functional role(s) Magoh exerted during nervous system development and evolution.

中文翻译：

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EJC成分Magoh在非脊椎动物的脊索动物中。

最早的颅骨具有新扩大的，精心制作的前脑，具有新的细胞类型和神经元网络。脊椎动物进化中的一个关键问题是这种大脑扩张何时以及如何发生。外显子连接复合体（EJC）在所有Eukarya的mRNA加工中都起着至关重要的作用。最近，有人提出，EJC可以抑制氘核吻合口中的递归RNA剪接，暗示着人类的脑部疾病如小头畸形和抑郁症。然而，EJC或EJC亚基对非椎体氘化口琴大脑发育的贡献仍然未知。而有志于脊索动物文字的演变，我们集中在模式植物，文昌鱼（Cephalochordata）和玻璃海鞘罗布斯塔（Tunicata），旨在研究Magoh直系同源基因的祖先和衍生表达状态。这项研究表明，Magoh仅属于脊椎动物的保守同语群的一部分，并暗示Magoh在哺乳动物中经历了复制和丢失事件。在文昌鱼和海鞘的早期发育过程中，Magoh基因在各种类型的祖细胞和组织中的母体贡献和合子表达与其他Bilateria中观察到的情况一致。在以后的开发中，我们还显示了Magoh在头孢酸盐和海鞘幼虫的大脑中的表达。总的来说，这些结果为进一步定义哪些职能角色提供了基础。Magoh在神经系统发育和进化过程中发挥作用。