Segmentation during regeneration in annelids

在动物界中，沿身体前后轴线的节段广泛存在于各种物种中，包括脊椎动物、节肢动物和环节动物。目前尚不清楚这些动物是否分享了身体分割的机制，或者这种分割模式是否在动物进化过程中独立出现。虽然在果蝇和脊椎动物中调节这种片段的分子机制已经得到了很好的研究，但环节动物的分子机制仍然不确定。我们推测，环节动物的节段研究将提供关于动物在进化过程中如何进化其身体模式的有价值的信息。我们利用最近在日本发现的一种具有强大再生能力的小蠕虫Enchytraeus Japan onensis，来了解它们的节段体是如何在再生过程中建立起来的。我们通过消减杂交技术和组织切片原位杂交技术鉴定了在再生过程中特异表达的cDNA。此外，我们还检测了果蝇或脊椎动物中已知的参与分割的基因的表达，如Delta、Notch和Wingless(Wnt)。我们还没有发现这些基因表达的片段模式，这意味着蠕虫中的片段受到与苍蝇和脊椎动物不同的机制的调节。

Segmentation along the antero-posterior axis of the body is seen in a wide range of species in animal kingdom, including vertebrates, arthropods, and annelids. It remains unknown whether the mechanisms underlying the body segmentation are shared by these animals, or whether the segmental pattern emerged independently during animal evolution. Whereas the molecular mechanisms by which the segmentation is regulated have well been studied in Drosophila and vertebrates, those for annelids remain undetermined. We reasoned that the study of segmentation in annelids will provide valuable information concerning how the animals evolved their body pattern during evolution. We used Enchytraeus japonensis, a small worm recently found in Japan, which is endowed with a powerful capability of regeneration, to understand how their segmented body is established during regenerative processes. We identified cDNAs that were specifically expressed during the regeneration by subtractive hybridization technique, and also by in situ hybridization in histological sections. In addition, we, examined expression of genes known to be involved in the segmentation in Drosophila or vertebrates, such as Delta, Notch, and Wingless (Wnt). We have not found a segmented pattern expressed by these genes, implying that the segmentation in worms is regulated by distinct mechanisms from those in flies and vertebrates.