SOMATIC MUTATION OF AN ANTIBODY TRANSGENE

在B细胞分化过程中，抗体基因通过一种特异性的免疫反应而多样化。 不同的机制。 B细胞早期 发展，V（D）J重组导致巨大的多样性 在成熟的B细胞中的Ig V区序列。 在后来的抗原依赖性B细胞分化阶段， 另一种机制，体细胞超突变，引起额外的 抗体多样性体细胞超变似乎是 使身体产生高亲和力的抗体反应， 防止病原体。 另一方面， 超突变也与异常激活 肿瘤发生中的癌基因，在一些B细胞 白血病，体细胞超突变显然正在进行，租赁， 肿瘤细胞的变异，可以击败基于抗- 独特型试剂 我们对这种分子结构知之甚少 参与体细胞超突变的机制 过程 我们最近发现， 类似的基因转换事件可以发生在小鼠体内， 抗体H链转基因，这些序列转移 与体细胞超突变过程有关 我们现在认为 基因转换机制可能是 超突变机制 在拟议项目期间， 我们希望研究转基因的靶向性和机制， 序列转移，并确定B细胞的类型， 序列传输事件。 我们还将进一步调查 序列转移与体细胞生物学的关系 超突变过程 本提案的目标是（1） 为了确定转基因序列转移是否通过基因 转化或DNA重组，（2）研究 VDJ之间转基因转化频率的间隔 节段，（3）定位和表征那些B细胞， 进行转基因转换，并研究 转基因转化和体细胞超突变，以及（4） 抗体V（D）J片段间序列转移研究 在内源性鼠IgH基因座内。 我们预计这些 研究将表明基因转换是否可能在 正常抗体基因的多样性和是否 转换涉及到目前尚未表征的机制 体细胞超变的证据 我们希望， 对超突变过程的理解可能会带来更多 治疗某些B细胞癌的有效方法以及 更全面地了解肿瘤发生的一些步骤。

During B Cell differentiation, antibody genes are diversified by a number of distinct mechanisms. At early stages of B-cell development, V(D)J recombination leads to an enormous diversity of lg V-region sequences among individual maturing B cells. During later, antigen-dependent, stages of B cell differentiation, another mechanisms, somatic hypermutation, gives rise to additional antibody diversity. Somatic hypermutation appears to be central in allowing the body to produce high-affinity antibody responses to protect against pathogens. On the other hand, somatic hypermutation has also been implicated in aberrantly activating oncogenes involved in tumorigenesis, and, in some B-cell leukemias, somatic hypermutation is apparently ongoing, leasing to tumor cell variations that can defeat therapies based on anti- idiotypic reagents. Very little is known about the molecular mechanisms that are involved in the somatic hypermutational process. We have recently found that sequence transfers which resemble gene conversion events can occur within a murine antibody H-chain transgene and that these sequence transfers correlate with the somatic hypermutation process. We now believe that gene conversion mechanisms could be a part of the somatic hypermutational mechanism. During the proposed project period, we wish to investigate the targeting and mechanism of transgene sequence transfers and determine the types of B cells that undergo sequence transfer events. We will also further investigate the relationships between the sequence transfer and somatic hypermutation processes. The goals of the current proposal are (1) to determine whether transgene sequence transfers occur by gene conversion or DNA recombination, (2) to investigate the effect of spacing on the frequency of transgene conversion between VDJ segments, (3) to localize and characterize those B cells which have undergone transgene conversion and investigate the correlation of transgene conversion and somatic hypermutation, and (4) to investigate sequence transfer among antibody V(D)J segments within the endogenous murine lgH locus. We expect that these studies will indicate whether gene conversion might have a role in the diversification of normal antibody genes and whether gene conversion is involved in the currently uncharacterized mechanism of somatic hypermutation. We hope that a more thorough understanding of the hypermutational process could lead to more effective approaches to treatment of some B cell cancers and to a fuller understanding of some steps of tumorigenesis.