動物體內,，中樞神經系統(tǒng)（central nervous system,；CNS）的進化問題困擾了科學家們好幾個世紀。脊椎動物,、昆蟲和環(huán)節(jié)動物都從同一個祖先那進化而來,，但是他們的CNS卻是截然不同?？茖W家們甚至認為CNS是在他們于進化樹上分道揚鑣之后才各自進化出的產物?，F(xiàn)在，來自海德堡的歐洲分子生物學實驗室（European Molecular Biology Laboratory,；EMBL）的研究者發(fā)現(xiàn),，脊椎動物的神經系統(tǒng)的歷史可能比預想的要早一些。發(fā)表在《Cell》雜志上的這篇文章,，暗示著脊椎動物,、昆蟲和環(huán)節(jié)動物的最后的共同祖先，已經具有與當今脊椎動物類似的中央集中的神經系統(tǒng)了,。
許多動物都進化出復雜的神經系統(tǒng),，但是物種之間的結構卻是可以不相同的，例如脊椎動物在背部有脊髓一般的中樞神經系統(tǒng),，昆蟲和環(huán)節(jié)蟲（Annelid Worm,；如蚯蚓）的神經細胞卻集中在腹部中類似于繩索梯子一般的神經節(jié)中。其他的一些無脊椎動物,，神經細胞會分散在全身各處,。但所有這些物種都起源于一個共同的祖先,，即對稱動物urbilateria。如果這個祖先已經擁有了神經系統(tǒng),，那么它的形狀是怎么樣的,？它是如何進化出今天動物體內如此千變萬化的神經系統(tǒng)的？這些都是Detlev Arendt和他的同事迫切想解答的問題,。為此,，他們深入研究了海生環(huán)節(jié)動物沙蠶Platynereis dumerilii的神經系統(tǒng)。
原始出處:
Cell, Vol 129, 277-288, 20 April 2007
Article
Molecular Architecture of Annelid Nerve Cord Supports Common Origin of Nervous System Centralization in Bilateria
Alexandru S. Denes,1,6 Gáspár Jékely,1,6 Patrick R.H. Steinmetz,1,4 Florian Raible,1 Heidi Snyman,1 Benjamin Prud'homme,2,5 David E.K. Ferrier,3 Guillaume Balavoine,2 and Detlev Arendt1,
1 Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, 69117, Germany
2 Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette 91198, France
3 Department of Zoology, University of Oxford, Oxford, OX1 3PS, United Kingdom
Corresponding author
Detlev Arendt
[email protected]
Summary
To elucidate the evolutionary origin of nervous system centralization, we investigated the molecular architecture of the trunk nervous system in the annelid Platynereis dumerilii. Annelids belong to Bilateria, an evolutionary lineage of bilateral animals that also includes vertebrates and insects. Comparing nervous system development in annelids to that of other bilaterians could provide valuable information about the common ancestor of all Bilateria. We find that the Platynereis neuroectoderm is subdivided into longitudinal progenitor domains by partially overlapping expression regions of nk and pax genes. These domains match corresponding domains in the vertebrate neural tube and give rise to conserved neural cell types. As in vertebrates, neural patterning genes are sensitive to Bmp signaling. Our data indicate that this mediolateral architecture was present in the last common bilaterian ancestor and thus support a common origin of nervous system centralization in Bilateria.
