Deep conservation of wrist and digit enhancers in fish.
鱼类腕部与指部增强子的深度保守性

Authors / 作者: Gehrke AR, Schneider I, de la Calle-Mustienes E, Tena JJ, Gomez-Marin C, Chandran M, Nakamura T, Braasch I, Postlethwait JH, Gómez-Skarmeta JL, Shubin NH.
Journal / 期刊: Proceedings of the National Academy of Sciences of the United States of America
Year / 年份: 2015
DOI: 10.1073/pnas.1420208112
Publisher / 出版社: https://www.pnas.org/doi/10.1073/pnas.1420208112
Abstract source / 摘要来源: https://europepmc.org/article/MED/25535365

Author abstract / 作者原文摘要
There is no obvious morphological counterpart of the autopod (wrist/ankle and digits) in living fishes. Comparative molecular data may provide insight into understanding both the homology of elements and the evolutionary developmental mechanisms behind the fin to limb transition. In mouse limbs the autopod is built by a "late" phase of Hoxd and Hoxa gene expression, orchestrated by a set of enhancers located at the 5' end of each cluster. Despite a detailed mechanistic understanding of mouse limb development, interpretation of Hox expression patterns and their regulation in fish has spawned multiple hypotheses as to the origin and function of "autopod" enhancers throughout evolution. Using phylogenetic footprinting, epigenetic profiling, and transgenic reporters, we have identified and functionally characterized hoxD and hoxA enhancers in the genomes of zebrafish and the spotted gar, Lepisosteus oculatus, a fish lacking the whole genome duplication of teleosts. Gar and zebrafish "autopod" enhancers drive expression in the distal portion of developing zebrafish pectoral fins, and respond to the same functional cues as their murine orthologs. Moreover, gar enhancers drive reporter gene expression in both the wrist and digits of mouse embryos in patterns that are nearly indistinguishable from their murine counterparts. These functional genomic data support the hypothesis that the distal radials of bony fish are homologous to the wrist and/or digits of tetrapods.

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
功能基因组实验在斑点雀鳝及斑马鱼中识别出 HoxA 和 HoxD 增强子。雀鳝序列能在小鼠腕部与手指区域驱动与小鼠增强子近似的表达，鱼类增强子也在胸鳍远端发挥作用。
Functional genomic assays identified HoxA and HoxD enhancers in spotted gar and zebrafish. Gar sequences drove reporter expression in mouse wrist and digit regions closely resembling mouse enhancer activity, while fish enhancers also acted in distal pectoral fins.

Conclusions / 结论
结果支持附肢远端调控机制的深度保守性，并与硬骨鱼远端辐状骨和四足动物腕部或指部结构同源的假说一致。
The findings support deep conservation of distal-appendage regulatory machinery and are consistent with homology between bony fish distal radials and tetrapod wrist or digit structures.

Relevance / 关联说明
直接研究清单物种，或研究广义类群中的代表物种。
Direct research on the listed species or a representative of the broadly named group.