Molecular and Functional Characterization of an Ancient Histocompatibility System

无脊椎的群体无脊椎动物在坚硬的表面上生长时，经常遇到自己物种的成员。这种遭遇的性质和结果是由高度歧视性的识别系统调节的。一般来说，近亲融合，而不相关的群体排斥。这些组织相容性现象已经在所有主要的无脊椎动物群体中明确地观察到，并引起了各种生物学学科的注意。特别是，它们通常被认为反映了脊椎动物免疫系统的进化起源，并在进化理论和生态学中发挥了突出作用，作为物种内竞争相互作用的范例。尽管组织相容性的普遍存在及其假定的生物学重要性，但尚未在任何殖民地无脊椎动物中确定负责的基因和分子。群落水螅虫（刺胞目；水螅目）的组织相容性可能比任何其他群落无脊椎动物的组织相容性都要好。该反应是由在单个染色体间隔中编码的至少两个基因位点的剂量依赖性相互作用引起的。本项目旨在鉴定水螅属组织相容性基因并对其进行功能表征。具体来说，靠近目标基因的遗传标记将用于从水螅DNA文库中识别相关的基因组片段。合理的候选组织相容性基因将通过测序整个片段确定。候选基因随后将在体内敲除，以测试它们在组织相容性反应中的作用。无脊椎动物组织相容性分子的特征将证明有助于理解，在其最基本的水平上，同种生物之间竞争相互作用的本质。此外，它将解决长期以来关于脊椎动物免疫和无脊椎动物组织相容性之间进化关系的争论。该项目将通过开发新课程、为本科生提供研究机会以及招募和培训科学界代表性不足的群体，将研究和教育结合起来。

Sessile, colonial invertebrates often encounter members of their own species as they grow on hard surfaces. The nature and outcomes of such encounters are mediated by highly discriminatory recognition systems. In general, close relatives fuse whereas unrelated colonies reject. These histocompatibility phenomena have been unambiguously observed in all major colonial invertebrate groups, and have attracted the attention of various biological disciplines. In particular, they are often claimed to reflect the evolutionary origins of the vertebrate immune system, and have played a prominent role in evolutionary theory and ecology as a paradigm of competitive interactions within species. Despite the prevalence of histocompatibility and their putative biological importance, the responsible genes and molecules have not been identified in any colonial invertebrate.Histocompatibility in the colonial hydroid Hydractinia symbiolongicarpus (Cnidaria; Hydrozoa) is better understood than in perhaps any other colonial invertebrate. The response results from a dose-dependent interaction of at least two gene loci encoded in a single chromosomal interval. This project aims to identify and functionally characterize the histocompatibility genes in Hydractinia. Specifically, genetic markers located at close proximity to the target genes will be used to identify the relevant genomic segment from a Hydractinia DNA library. Plausible candidate histocompatibility genes will be identified by sequencing the entire segment. Candidate genes will be subsequently knocked-out in vivo to test their role in histocompatibility responses. Characterization of the invertebrate histocompatibility molecules will prove instrumental for understanding, at its most basic level, the nature of competitive interactions amongst conspecifics. Furthermore, it will settle the long-standing debate on the evolutionary relationship between vertebrate immunity and invertebrate histocompatibility. The project will integrate research and education by developing new curricula, providing research opportunities for undergraduates, and recruiting and training underrepresented groups in science.