Sánchez-Soriano Natalia, Bottenberg Wolfgang, Fiala André, Haessler Ulrike, Kerassoviti Afroditi, Knust Elisabeth, Löhr Robert, Prokop Andreas
Faculty of Life Sciences, WTCCMR, The University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Dev Biol. 2005 Dec 1;288(1):126-38. doi: 10.1016/j.ydbio.2005.09.026. Epub 2005 Oct 11.
Dendrites represent arborising neurites in both vertebrates and invertebrates. However, in vertebrates, dendrites develop on neuronal cell bodies, whereas in higher invertebrates, they arise from very different neuronal structures, the primary neurites, which also form the axons. Is this anatomical difference paralleled by principal developmental and/or physiological differences? We address this question by focussing on one cellular model, motorneurons of Drosophila and characterise the compartmentalisation of these cells. We find that motorneuronal dendrites of Drosophila share with typical vertebrate dendrites that they lack presynaptic but harbour postsynaptic proteins, display calcium elevation upon excitation, have distinct cytoskeletal features, develop later than axons and are preceded by restricted localisation of Par6-complex proteins. Furthermore, we demonstrate in situ and culture that Drosophila dendrites can be shifted from the primary neurite to their soma, i.e. into vertebrate-like positions. Integrating these different lines of argumentation, we propose that dendrites in vertebrates and higher invertebrates have a common origin, and differences in dendrite location can be explained through translocation of neuronal cell bodies introduced during the evolutionary process by which arthropods and vertebrates diverged from a common urbilaterian ancestor. Implications of these findings for studies of dendrite development, neuronal polarity, transport and evolution are discussed.
在脊椎动物和无脊椎动物中，树突均代表呈树枝状分布的神经突。然而，在脊椎动物中，树突在神经元细胞体上发育，而在高等无脊椎动物中，它们起源于截然不同的神经元结构——初级神经突，初级神经突同时也形成轴突。这种解剖学上的差异是否伴随着主要的发育和/或生理差异呢？我们通过聚焦于一个细胞模型——果蝇的运动神经元来探讨这个问题，并对这些细胞的区室化进行了表征。我们发现，果蝇的运动神经元树突与典型的脊椎动物树突具有以下共同特征：它们缺乏突触前蛋白，但含有突触后蛋白，在受到刺激时会出现钙离子浓度升高，具有独特的细胞骨架特征，比轴突发育得晚，并且在其之前有Par6复合体蛋白的局限性定位。此外，我们在原位和培养实验中证明，果蝇的树突可以从初级神经突转移到它们的细胞体上，即转移到类似脊椎动物的位置。综合这些不同的论证思路，我们提出脊椎动物和高等无脊椎动物的树突有共同的起源，树突位置的差异可以通过在进化过程中引入的神经元细胞体的移位来解释，在这个进化过程中，节肢动物和脊椎动物从共同的双侧对称祖先分化而来。我们还讨论了这些发现对树突发育、神经元极性、运输和进化研究的意义。
