Isotype Exclusion and Hypermutation in the Nurse Shark

描述(申请人提供)：鲨鱼和溜冰鞋是最早的脊椎动物的代表，其免疫系统基于免疫球蛋白(Ig)受体，通过基因重排和体细胞突变而多样化。这两个过程中涉及的识别基序和酶机制指向了独立出现的机械上不相关的途径。我们假设，在鲨鱼之前，原型抗原受体可能只是通过突变而多样化；重排的机制是在后来的进化中引入的，并不是表达调控过程的内在部分。我们建议： (1)研究重排在鲨鱼中的作用，鲨鱼携带多个Ig基因座和生殖系重排基因。我们将确定鲨鱼Ig受体是否克隆表达，许多基因座之间是否存在激活等级，以及生殖系或体细胞的生产性重排是否反馈调节其他受体的表达。 (2)研究L链突变的一种新机制--非模板插入。我们的目标是研究变化的模式，以确定这种结构是如何在超突变过程中形成的。我们还将研究H链突变，以获得这种早期脊椎动物物种体细胞过度突变的全面图像。 这项研究提供的信息将为抗体多样化机制的进化和重排过程提供新的理解，并使人们对致病非我的特定克隆识别的出现有更深入的了解。

DESCRIPTION (provided by applicant): Sharks and skates are representatives of the earliest vertebrates with an immune system based on immunoglobulin (Ig) receptors that diversify by gene rearrangement and somatic mutation. The recognition motifs and enzymatic machinery involved in the two processes point to mechanistically unrelated pathways that arose independently. We hypothesize that, before sharks, the prototype antigen receptor may have diversified only by mutation; the mechanism of rearrangement became introduced later in evolution and is not an intrinsic part of the regulatory process for expression. We propose to: (1) investigate the role of rearrangement in the shark, which carries multiple Ig loci and germline-rearranged genes. We will establish whether the shark Ig receptors are clonally expressed, if there is a hierarchy of activation among the many loci, and if productive rearrangements, germline or somatic, feed back to modulate expression of others. (2) investigate a novel mechanism in L chain mutants, non-templated insertion. Our goal is to examine the patterns of change to determine how such structures are formed during the hypermutation process. We will also study H chain mutation, to obtain a comprehensive picture of somatic hypermutation in one species of this early vertebrate. The information emerging from this research will provide new understanding for the evolution of mechanisms for antibody diversification and the rearrangement process and give insight into the emergence of a specific, clonal recognition of the pathogenic non-self.