Multiple IgH Isotypes Including IgD, Subclasses of IgM, and IgY Are Expressed in the Common Ancestors of Modern Birds
Multiple IgH Isotypes Including IgD, Subclasses of IgM, and IgY Are Expressed in the Common Ancestors of Modern Birds
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现代鸟类的共同祖先中表达了多种 IgH 同型，包括 IgD、IgM 亚类和 IgY
DOI：
10.4049/jimmunol.1600307
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发表时间：
2016-06-15
影响因子：
4.4
通讯作者：
Zhao, Yaofeng
中科院分区：
文献类型：
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作者：
Han, Binyue;Yuan, Hui;Zhao, Yaofeng
虽然在进化上与IgM一样古老，但多年来人们一直认为IgD不存在于鸟类中。基于最近测序的48种鸟类的基因组以及免疫相关组织的高通量转录组测序，我们证明在这项工作中，鸵鸟（鸵鸟骆驼）具有功能性δ基因，编码一个膜结合的IgD H链与7个CH结构域。此外，在许多其他鸟类物种中也清楚地鉴定出了delta序列，这表明delta基因在鸟类中广泛分布，仅在某些鸟类物种中不存在。我们还表明，鸵鸟拥有两个μ基因（mu 1，mu 2）和两个nu基因（nu 1，nu 2），除了d和a基因。系统发育分析表明，亚类多样化的mu和nu基因发生在鸟类进化的早期阶段，从非鸟类爬行动物的分歧。虽然两个nu基因的位置是未知的，物理作图表明，其余的基因是按照mu 1-delta-alpha-mu 2的顺序组织的，alpha基因相对于其他基因是反向的。与以前的研究一起，我们的数据表明，鸟类和非鸟类爬行动物物种最有可能共享一个共同的祖先IgH基因位点，包含一个δ基因和一个倒α基因。然后，δ基因在特定的鸟类中丢失，而α基因在特定的非鸟类爬行动物中丢失。在这项研究中获得的数据提供了重要的见解IgH基因的进化在四足动物的理解。
Although evolutionarily just as ancient as IgM, it has been thought for many years that IgD is not present in birds. Based on the recently sequenced genomes of 48 bird species as well as high-throughput transcriptome sequencing of immune-related tissues, we demonstrate in this work that the ostrich (Struthio camelus) possesses a functional delta gene that encodes a membrane-bound IgD H chain with seven CH domains. Furthermore, delta sequences were clearly identified in many other bird species, demonstrating that the delta gene is widely distributed among birds and is only absent in certain bird species. We also show that the ostrich possesses two mu genes (mu 1, mu 2) and two nu genes (nu 1, nu 2), in addition to the d and a genes. Phylogenetic analyses suggest that subclass diversification of both the mu and nu genes occurred during the early stages of bird evolution, after their divergence from nonavian reptiles. Although the positions of the two nu genes are unknown, physical mapping showed that the remaining genes are organized in the order mu 1-delta-alpha-mu 2, with the alpha gene being inverted relative to the others. Together with previous studies, our data suggest that birds and nonavian reptile species most likely shared a common ancestral IgH gene locus containing a delta gene and an inverted alpha gene. The delta gene was then evolutionarily lost in selected birds, whereas the alpha gene lost in selected nonavian reptiles. The data obtained in this study provide significant insights into the understanding of IgH gene evolution in tetrapods.