比目鱼类的眼睛移位和不对称的进化起源

比目鱼类外形不对称产生的机制引起人们兴趣已逾一个多世纪。从比目鱼类(鲽形目)的类群和分布、变态过程中眼睛移位机械力的来源、甲状腺激素调控眼睛移位的信号通路、比目鱼类外形左右不对称与内脏左右不对称两者调控机制之间的关系以及比目鱼类眼睛左右不对称的进化起源等5个方面,系统地介绍了比目鱼类变态发育过程中眼睛移位的研究历史。重点介绍了本实验室提出的关于眼睛移位的组织学模型,以及眼睛移位信号调控途径的最新研究进展。发现并证明眶下皮肤组织细胞分裂导致眼睛移动,而眼睛移动进一步导致额骨变形,纠正了以往假说的谬误。最后,对比目鱼类眼睛移位和不对称进化起源进行了探讨,提出了解释比目鱼类不对称进化起源的新假说。

The eye migration and evolutionary origin of flatfish asymmetry

Asymmetry of flatfish has already caught people’s eye over one century.The research on eye migration is introducted as five sections in this review: diversity and distribution of Pleuronectiformes,the mechanical force driving eye migration,thyroid hormone-dependent signalling pathway in regulating eye migration,the relationship between eye migration and the left/right asymmetry of visceral organs,and evolutionary origin of flatfish asymmetry.My lab’s findings on the genetic mechanism behind eye migration are introducted extensively,such as our important finding that eye migration is driven by proliferating cells in suborbital skin and the twist of frontal bone is dependent upon eye migration,which corrected some mistakes of previous hypothesis.Thyroid hormone-dependent signalling pathway was investigated extensively as well.T3 distribution and expressional location of type 2 deiodinase and thyroid hormone receptor(TRαA and TRβ1) in the skin around both eyes displayed left/right and dorsal/ventral asymmetry pattern,which is similar as observed pattern of proliferating cells in same area in previous study.The TH-dependent signalling pathway in regulating eye migration might be T4-Dio2-T3-TRαA/TRβ1.Finally,we propose a hypothesis on evolutionary origin of flatfish asymmetry,and hope that this could arouse further discussion on the flatfish evolution.