Stewart Thomas A, Bhat Ramray, Newman Stuart A
Department of Ecology and Evolutionary Biology, Yale University, 300 Heffernan Dr, West Haven, CT 06515 USA.
Minnesota Center for Philosophy of Science, University of Minnesota, 746 Heller Hall, 271 19th Ave. S, Minneapolis, MN 55455 USA.
Evodevo. 2017 Nov 21;8:21. doi: 10.1186/s13227-017-0084-8. eCollection 2017.
The evolution of tetrapod limbs from paired fins has long been of interest to both evolutionary and developmental biologists. Several recent investigative tracks have converged to restructure hypotheses in this area. First, there is now general agreement that the limb skeleton is patterned by one or more Turing-type reaction-diffusion, or reaction-diffusion-adhesion, mechanism that involves the dynamical breaking of spatial symmetry. Second, experimental studies in finned vertebrates, such as catshark and zebrafish, have disclosed unexpected correspondence between the development of digits and the development of both the endoskeleton and the dermal skeleton of fins. Finally, detailed mathematical models in conjunction with analyses of the evolution of putative Turing system components have permitted formulation of scenarios for the stepwise evolutionary origin of patterning networks in the tetrapod limb. The confluence of experimental and biological physics approaches in conjunction with deepening understanding of the developmental genetics of paired fins and limbs has moved the field closer to understanding the fin-to-limb transition. We indicate challenges posed by still unresolved issues of novelty, homology, and the relation between cell differentiation and pattern formation.
四足动物的四肢从成对的鳍进化而来，长期以来一直引起进化生物学家和发育生物学家的兴趣。最近的几条研究路径汇聚在一起，重塑了该领域的假说。首先，现在人们普遍认为，肢体骨骼是由一种或多种图灵型反应扩散或反应扩散-黏附机制形成的，这种机制涉及空间对称性的动态打破。其次，对有鳍脊椎动物（如猫鲨和斑马鱼）的实验研究揭示了手指发育与鳍的内骨骼和真皮骨骼发育之间意想不到的对应关系。最后，详细的数学模型与对假定的图灵系统组件进化的分析相结合，使得人们能够为四足动物肢体模式化网络的逐步进化起源制定各种设想。实验方法与生物物理方法的融合，以及对成对鳍和四肢发育遗传学的深入理解，使该领域更接近于理解鳍到四肢的转变。我们指出了新颖性、同源性以及细胞分化与模式形成之间关系等尚未解决的问题所带来的挑战。
