Segmentation during regeneration in annelids

在动物界的许多物种中，包括脊椎动物、节肢动物和环节动物，都可以看到沿身体前后轴的分割。目前尚不清楚这些动物是否有共同的身体分割机制，或者这种分割模式是否在动物进化过程中独立出现。尽管在果蝇和脊椎动物中已经很好地研究了分割调节的分子机制，但在环节动物中仍然不确定。我们认为，研究环节动物的分割将为研究动物在进化过程中如何进化它们的身体模式提供有价值的信息。我们以日本最近发现的一种具有强大再生能力的小蠕虫encytraeus japonensis为研究对象，来了解它们的分节体是如何在再生过程中形成的。我们通过减法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性表达的cdna。此外，我们还检测了在果蝇或脊椎动物中已知参与分割的基因的表达，如Delta、Notch和Wingless （Wnt）。我们没有发现这些基因表达的片段模式，这意味着蠕虫的片段受不同于果蝇和脊椎动物的机制的调节。

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.