University of Hamburg, Biozentrum Grindel und Zoologisches Museum, Hamburg, Germany.
Heredity (Edinb). 2010 Nov;105(5):413-22. doi: 10.1038/hdy.2009.184. Epub 2010 Jan 13.
Cave fish provide a model system for exploring the genetic basis of regressive evolution. A proposal that regressive evolution (for example, eye loss) may result from pleiotropy, by selection on constructive traits (for example, improved taste) has received considerable recent interest as it contradicts the theory that regressive evolution results from neutral evolution. In this study, these theories are reviewed by placing the classical and molecular genetic studies of cave fish in a common framework. Sequence data and the wide range of intermediate sized eyes in hybrids between surface and cave fish suggest that currently there is no strong evidence supporting the notion that structural eye genes have been afflicted by destructive mutations. The hedgehog genes, which are suggested to reduce the primordial eye cup size in cavefish by expanded expression, are also not mutated. The as yet unidentified 'eye genes' revealed by crossing experiments seem primarily responsible for eye regression and determine eye development through hedgehog. Hybrids between different eye-reduced cave populations developing large 'back to surface eyes' support this. In such eyes, hh expression is restored by complementary restitution because of the recombination of 'eye genes', which were subjected to different destructive mutations in separately evolving cave fish populations. All regressive and constructive cave fish traits can be considered to result from genetic modules, each showing a comparable pattern of expression. The constructive and regressive modules are shown to inherit independently from each other, which does not support the view that eye regression is a spin off effect of the improvement of beneficial traits through pleiotropy.
洞穴鱼为探索退行性进化的遗传基础提供了一个模型系统。有一种观点认为，退行性进化（例如眼睛退化）可能是由多效性引起的，即通过对建设性特征（例如，味觉改善）的选择。最近，这种观点引起了相当大的关注，因为它与退行性进化是由中性进化引起的理论相矛盾。在这项研究中，通过将洞穴鱼的经典和分子遗传学研究置于一个共同的框架中，对这些理论进行了回顾。序列数据和表面鱼与洞穴鱼杂交种中广泛存在的中等大小眼睛表明，目前没有强有力的证据支持结构性眼睛基因受到破坏性突变影响的观点。被认为通过扩展表达减少洞穴鱼原始眼睛杯大小的刺猬基因也没有突变。通过杂交实验揭示的尚未确定的“眼睛基因”似乎主要负责眼睛退化，并通过刺猬基因决定眼睛发育。不同眼睛退化的洞穴种群之间的杂交种发展出大的“回到表面的眼睛”支持这一观点。在这样的眼睛中，由于“眼睛基因”的重组，hh 表达通过互补恢复，“眼睛基因”在分别进化的洞穴鱼种群中受到不同的破坏性突变。所有退行性和建设性的洞穴鱼特征都可以被认为是由遗传模块产生的，每个模块都表现出类似的表达模式。建设性和退行性模块被证明彼此独立遗传，这并不支持这样的观点，即眼睛退化是通过多效性改善有益特征的副产品。
