Appendage expression driven by the Hoxd Global Control Region is an ancient gnathostome feature.
由 Hoxd 全局调控区驱动的附肢表达是有颌类的古老特征

Authors / 作者: Schneider I, Aneas I, Gehrke AR, Dahn RD, Nobrega MA, Shubin NH.
Journal / 期刊: Proceedings of the National Academy of Sciences of the United States of America
Year / 年份: 2011
DOI: 10.1073/pnas.1109993108
Publisher / 出版社: https://www.pnas.org/doi/10.1073/pnas.1109993108
Abstract source / 摘要来源: https://europepmc.org/article/MED/21765002

Author abstract / 作者原文摘要
The evolutionary transition of the fins of fish into tetrapod limbs involved genetic changes to developmental systems that resulted in novel skeletal patterns and functions. Approaches to understanding this issue have entailed the search for antecedents of limb structure in fossils, genes, and embryos. Comparative genetic analyses have produced ambiguous results: although studies of posterior Hox genes from homology group 13 (Hoxa-13 and Hoxd-13) reveal similarities in gene expression between the distal segments of fins and limbs, this functional homology has not been supported by genomic comparisons of the activity of their cis-regulatory elements, namely the Hoxd Global Control Region. Here, we show that cis-regulatory elements driving Hoxd gene expression in distal limbs are present in fish. Using an interspecies transgenesis approach, we find functional conservation between gnathostome Hoxd enhancers, demonstrating that orthologous sequences from tetrapods, zebrafish and skate can drive reporter gene expression in mouse limbs and zebrafish fins. Our results support the notion that some of the novelties associated with tetrapod limbs arose by modification of deeply conserved cis- and trans-acting mechanisms of Hox regulation in gnathostomes.

Summary basis / 解读依据
摘要解读依据已查看的索引作者摘要；如已保存全文，可用于进一步阅读。
Summary based on the inspected indexed author abstract; archived full text, when available, is provided for further reading.

Key findings / 主要发现
跨物种转基因实验显示，四足动物、斑马鱼及鳐类的同源 Hoxd 增强子能在小鼠肢体与斑马鱼鳍中驱动报告基因表达，因此与附肢远端相关的调控活性早于四足动物肢体出现。
Cross-species transgenic experiments showed that homologous Hoxd enhancer sequences from tetrapods, zebrafish and skate can drive reporter expression in mouse limbs and zebrafish fins. Regulatory activity associated with distal appendages therefore predates the evolution of tetrapod limbs.

Conclusions / 结论
四足动物肢体创新部分源于对深度保守 Hox 调控机制的修改，而非完全新建调控系统；本篇以鳐类作为多物种比较实验材料之一。
Tetrapod limb innovations partly arose by modifying deeply conserved Hox regulatory mechanisms, rather than requiring an entirely new regulatory system. Skate is a comparative experimental source within this multispecies study.

Relevance / 关联说明
鳐类增强子作为多物种鳍肢过渡研究的实验比较材料。
Skate enhancer sequences are experimental comparators in a multispecies fin-to-limb study.