Pleiotropic functions of embryonic sonic hedgehog expression link jaw and taste bud amplification with eye loss during cavefish evolution
Pleiotropic functions of embryonic sonic hedgehog expression link jaw and taste bud amplification with eye loss during cavefish evolution
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DOI：
10.1016/j.ydbio.2009.03.003
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发表时间：
2009-06-01
影响因子：
2.7
通讯作者：
Jeffery, William R.
中科院分区：
文献类型：
--
作者：
Yamamoto, Yoshiyuki;Byerly, Mardi S.;Jeffery, William R.
本研究探讨了音刺猬（shh）在增加口咽建设性的特点（下巴和味蕾）在牺牲眼睛的盲洞穴鱼Astyanax mexicanus的作用。在洞穴鱼胚胎中，眼睛原基在过度活跃的Shh信号的影响下退化。在音乐会上，洞穴鱼显示放大下巴的大小和味蕾的数量作为改变进食行为的一部分。为了确定是否多效性效应的过度活跃的Shh信号链接这些回归和建设性的特点，shh表达进行了比较，在后期发展的表面居住（表面鱼）和洞穴居住（洞穴鱼）形式的Astyanax。经过最初的扩张沿着中线的早期胚胎，shh升高，在口咽区的洞穴鱼，后来被限制在味蕾。Shh抑制和过表达实验结果表明Shh信号在口腔和味蕾发育中具有重要作用。在发育的特定时期注射shh转基因的条件性过表达表明，味蕾扩增和眼退化在同一发育早期对shh过表达敏感，尽管味蕾直到很晚才形成。洞穴鱼和表面鱼之间的遗传杂交揭示了眼睛大小和下巴大小/味蕾数量之间的反比关系，支持口咽建设性特征和眼睛退化之间的联系。结果表明，过度活跃的Shh信号增加了洞穴鱼的口腔和味蕾放大，而牺牲了眼睛。因此，建设性的口咽性状的选择可能是负责眼损失在洞穴鱼类进化过程中通过多效性功能的Shh信号通路。(C)2009 Elsevier Inc. All rights reserved.
This study addresses the role of sonic hedgehog (shh) in increasing oral-pharyngeal constructive traits (jaws and taste buds) at the expense of eyes in the blind cavefish Astyanax mexicanus. In cavefish embryos, eye primordia degenerate under the influence of hyperactive Shh signaling. In concert, cavefish show amplified jaw size and taste bud numbers as part of a change in feeding behavior. To determine whether pleiotropic effects of hyperactive Shh signaling link these regressive and constructive traits, shh expression was compared during late development of the surface-dwelling (surface fish) and cave-dwelling (cavefish) forms of Astyanax. After an initial expansion along the midline of early embryos, shh was elevated in the oral-pharyngeal region in cavefish and later was confined to taste buds. The results of shh inhibition and overexpression experiments indicate that Shh signaling has an important role in oral and taste bud development. Conditional overexpression of an injected shh transgene at specific times in development showed that taste bud amplification and eye degeneration are sensitive to shh overexpression during the same early developmental period, although taste buds are not formed until much later. Genetic crosses between cavefish and surface fish revealed an inverse relationship between eye size and jaw size/taste bud number, supporting a link between oral-pharyngeal constructive traits and eye degeneration. The results suggest that hyperactive Shh signaling increases oral and taste bud amplification in cavefish at the expense of eyes. Therefore, selection for constructive oral-pharyngeal traits may be responsible for eye loss during cavefish evolution via pleiotropic function of the Shh signaling pathway. (C) 2009 Elsevier Inc. All rights reserved.