Evidence of five digits in embryonic horses and developmental stabilization of tetrapod digit number
Evidence of five digits in embryonic horses and developmental stabilization of tetrapod digit number
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DOI：
10.1098/rspb.2019.2756
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发表时间：
2020-02-12
影响因子：
4.7
通讯作者：
Sears, Karen E.
中科院分区：
文献类型：
--
作者：
Kavanagh, Kathryn D.;Bailey, C. Scott;Sears, Karen E.
以前的工作比较马与其他哺乳动物的发育机制参与数字减少报告说，马只有一个“单一的数字”，与两个侧翼metapodial确定为残留的数字II和IV。在这里，我们表明，早期马胚胎经历了一个阶段，五个数字浓缩，侧翼夹板后足的融合的两个前数字I和II和两个后数字IV和V，在一个惊人的个体发育和胚胎发育之间的平行。考虑到即使是这种最极端的足趾减少病例也表现出原发性五趾畸形，我们重新检查了所有足趾减少的四足动物的足趾浓缩的初始阶段，并发现在所有情况下，五个或四个足趾开始（四个足趾I缺失）。马和其他趾减少的现代类群中持续的五趾起始强调了趾起始时的持久发育稳定性。数字进化模型可能有助于阐明器官系统变得高度稳定而不是高度可塑的生物环境。
Previous work comparing the developmental mechanisms involved in digit reduction in horses with other mammals reported that horses have only a 'single digit', with two flanking metapodials identified as remnants of digit II and IV. Here we show that early Equus embryos go through a stage with five digit condensations, and that the flanking splint metapodials result from fusions of the two anterior digits I and II and the two posterior digits IV and V, in a striking parallel between ontogeny and phylogeny. Given that even this most extreme case of digit reduction exhibits primary pentadactyly, we re-examined the initial stages of digit condensation of all digit-reduced tetrapods where data are available and found that in all cases, five or four digits initiate (four with digit I missing). The persistent pentadactyl initiation in the horse and other digit-reduced modern taxa underscores a durable developmental stability at the initiation of digits. The digit evodevo model may help illuminate the biological circumstances under which organ systems become highly stabilized versus highly plastic.