Arendt Detlev
European Molecular Biology Laboratory, Developmental Biology Programme, Heidelberg, Germany.
Int J Dev Biol. 2003;47(7-8):563-71.
The evolution of the eye is a matter of debate ever since Darwin's Origin of Species. While morphological comparisons of eye anatomy and photoreceptor cell types led to the view that animal eyes evolved multiple times independently, the molecular conservation of the pax6 eye-specifying cascade has indicated the contrary - that animal eyes evolved from a common, simple precursor, the proto-eye. Morphological and molecular comparative approaches are combined here in a novel Evo-Devo approach, the molecular comparison of cell types ("comparative molecular cell biology"). In the eye, the various types of photoreceptor cells, as well as pigment and lens cells, each require distinct combinations of specifying transcription factors that control their particular differentiation programmes, such as opsin expression in photoreceptors, specific neurotransmitter metabolism, or axonal outgrowth. Comparing the molecular combinatorial codes of cell types of animal extant eyes, their evolutionary histories can be reconstructed. This is exemplified here on the evolution of ciliary and rhabdomeric photoreceptor cells in bilaterian eyes and on the evolution of cell type diversity in the vertebrate retina. I propose that the retinal ganglion, amacrine and horizontal cells are evolutionary sister cell types that evolved from a common rhabdomeric photoreceptor cell precursor.
自达尔文的《物种起源》问世以来，眼睛的进化一直是个备受争议的问题。虽然对眼睛解剖结构和光感受器细胞类型的形态学比较得出了动物眼睛是多次独立进化的观点，但Pax6眼睛指定级联的分子保守性却表明了相反的情况——动物眼睛是从一个共同的、简单的前身——原眼进化而来的。本文将形态学和分子比较方法结合在一种新颖的演化发育生物学方法中，即细胞类型的分子比较（“比较分子细胞生物学”）。在眼睛中，各种类型的光感受器细胞以及色素细胞和晶状体细胞，各自都需要特定的转录因子组合来控制其特定的分化程序，例如光感受器中的视蛋白表达、特定的神经递质代谢或轴突生长。通过比较现存动物眼睛细胞类型的分子组合密码，可以重建它们的进化历史。本文以两侧对称动物眼睛中睫状和微绒毛状光感受器细胞的进化以及脊椎动物视网膜中细胞类型多样性的进化为例进行了说明。我认为视网膜神经节细胞、无长突细胞和水平细胞是从共同的微绒毛状光感受器细胞前体进化而来的进化姐妹细胞类型。
