A molecular analysis of ascidian metamorphosis reveals activation of an innate immune response.
A molecular analysis of ascidian metamorphosis reveals activation of an innate immune response.
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发表时间：
2002-10
期刊：
影响因子：
4.6
通讯作者：
B. Davidson;B. Swalla
中科院分区：
文献类型：
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作者：
B. Davidson;B. Swalla
海鞘变态代表了一个强大的模型，在脊索动物发展的比较工作，仍然很大程度上未被探索。我们通过抑制PCR法分离了分阶段幼虫和幼鱼的cdna，分离出了在变形过程中差异表达的转录本。我们采用了一系列的三次减法来解剖变态过程中的基因表达。我们分离了132个不同的蛋白质编码序列，其中65个转录本与GenBank蛋白显著匹配。其中一些基因被认为具有与关键变态事件相关的功能，包括平滑肌、血细胞、心脏组织和成体神经系统从幼虫雏形的分化。此外，很大一部分差异表达的转录本与先天免疫系统中鉴定的基因相匹配。先天免疫对病原体特异性分子和/或受损的自身组织给予快速反应。先天免疫基因在变态过程中的激活可能代表了成人免疫系统的程序性成熟。此外，这种免疫反应可能是吞噬和重组幼虫组织所必需的。先天免疫相关的炎症反应也可能是发生在游动幼虫期和定居后立即发生的两波跨表皮血细胞迁移的基础。我们对这些跨表皮迁移进行了表征，并发现一些迁移细胞完全通过外衣中的前通道离开动物。我们发现这些细胞定位于检测外部定居信号，并假设先天免疫系统也可能用于检测和快速响应环境定居信号。
Ascidian metamorphosis represents a powerful model for comparative work on chordate development that has remained largely unexplored. We isolated transcripts differentially expressed during metamorphosis in the ascidian Boltenia villosa by suppressive PCR subtractions of staged larval and juvenile cDNAs. We employed a series of three subtractions to dissect gene expression during metamorphosis. We have isolated 132 different protein coding sequences, and 65 of these transcripts show significant matches to GenBank proteins. Some of these genes have putative functions relevant to key metamorphic events including the differentiation of smooth muscle, blood cells, heart tissue and adult nervous system from larval rudiments. In addition, a significant fraction of the differentially expressed transcripts match identified genes from the innate immune system. Innate immunity confers a rapid response to pathogen-specific molecules and/or compromised self-tissues. The activation of innate immunity genes during metamorphosis may represent the programmed maturation of the adult immune system. In addition, this immune response may be necessary for phagocytosis and re-structuring of larval tissues. An innate immune-related inflammatory response may also underlie two waves of trans-epidermal blood cell migration that occur during the swimming larval period and immediately upon settlement. We characterized these trans-epidermal migrations and discovered that some migratory cells leave the animal entirely through an anterior tunnel in the tunic. We show that these cells are positioned to detect external settlement cues and hypothesize that the innate immune system may also be employed to detect and rapidly respond to environmental settlement cues.