Molecular Analyses of the individual function of the transcriptional Co-Activator BOB.1/OBF.1 in B versus T lymphocytes and its specific contribution to the Germinal Center Reaction

BOB.1/OBF.1最初被描述为B细胞特异性转录共激活因子。BOB.1/OBF.1本身与DNA的亲和力很弱，但会被转录因子Oct1和Oct2招募到所谓的八聚体基序中，从而增强八聚体依赖的转录。BOB.1/OBF.1缺陷小鼠在B细胞发育的不同阶段表现出严重的缺陷，但在某些T细胞群中也表现出严重的缺陷，如TH1、TH2或滤泡T辅助细胞(TFH)。BOB.1/OBF.1基因缺陷小鼠的主要特征是完全没有生发中心，因此也没有生发中心衍生的B细胞，如血浆和记忆B细胞。然而，生发中心的缺乏是否完全是由B细胞中BOB.1/OBF.1缺陷引起的，还是由低效的T细胞帮助，特别是由TFH提供的，是否也是导致这种严重表型的原因，这一问题尚不完全清楚。到目前为止，由于缺乏合适的工具来调控BOB.1/OBF.1在这些终末细胞分化阶段的表达，我们无法通过精确的分子分析来确定BOB.1/OBF.1对生发中心反应的确切影响。此外，在野生型B细胞存在的情况下，研究T细胞中BOB.1/OBF.1缺陷的选择有限，反之亦然。我们现在已经产生了携带BOB.1/OBF.1等位基因的小鼠。这样的小鼠系统允许有条件地删除BOB.1/OBF.1的表达，从而在没有转录共激活因子的情况下精确地分析B细胞和T细胞的分化和功能。利用我们的条件系统和适当表达Cre的小鼠系，我们现在能够分析BOB.1/OBF.1在B细胞发育早期和后期表达的特殊需要，以及BOB.1/OBF.1对特定T细胞亚群功能的要求。为了了解BOB.1/OBF.1在生理条件下对B细胞发育和功能的影响，我们的研究重点是鉴定和进一步鉴定BOB.1/OBF.1靶基因。此外，这些分析使我们能够理解如果BOB.1/OBF.1在定义的B和T细胞亚群中被完全删除，它将如何影响生发中心反应。此外，由于我们新生成的系统，我们现在能够表征BOB.1/OBF.1在免疫病理条件下的个体相关性，从而进一步阐明BOB.1/OBF.1在自身免疫过程中的作用。因此，本研究的目的是确定转录共激活因子BOB.1/OBF.1参与B和T细胞发育和分化的分子机制，以及BOB.1/OBF.1在生理和免疫病理条件下在这些过程中的新功能。

BOB.1/OBF.1 was originally described as a B cell specific transcriptional co-activator. BOB.1/OBF.1 itself has only very weak affinity to DNA but is recruited by the transcription factors Oct1 and Oct2 to the so called Octamer motif and thereby enhances Octamer-dependent transcription. BOB.1/OBF.1-deficient mice show severe defects at different stages of B cell development, but also in certain T cell populations, like TH1, TH2 or follicular T-helper cells (TFH). The main characteristic of BOB.1/OBF.1-deficient mice is the complete absence of germinal centers and consequently also of germinal center derived B cells, like plasma and memory B cells. However, the question is not fully understood, whether the lack of germinal centers is caused exclusively by the BOB.1/OBF.1 deficiency in B cells or if in addition an inefficient T cell help, provided particularly by TFH, also contributes to this severe phenotype. Because of the lack of appropriate tools to regulate BOB.1/OBF.1 expression in these terminal cell differentiation stages so far we were not able to define the exact impact of BOB.1/OBF.1 to the germinal center reaction by precise molecular analyses. Furthermore, there were only limited options to study BOB.1/OBF.1 deficiency in T cells in the presence of wildtype B cells and vice versa.We have now generated mice bearing floxed BOB.1/OBF.1 alleles. Such a mouse system allows the conditional deletion of BOB.1/OBF.1 expression and therefore the precise analyses of B- as well as T-cell differentiation and function in the absence of the transcriptional co-activator. Using our conditional system together with appropriate Cre expressing mouse lines we are now able to analyze the specific need of BOB.1/OBF.1 expression in early and also in late stages of B-cell development as well as the requirement of BOB.1/OBF.1 for the function of specific T cell subpopulations. A main focus of our project is the identification and further characterization of BOB.1/OBF.1 target genes in order to understand the influence of BOB.1/OBF.1 on B-cell development and function under physiological conditions. Moreover, these analyses allow us to understand how BOB.1/OBF.1 affects germinal center reaction if it is exclusively deleted in defined B and T cell subpopulations. Additionally, due to our newly generated system we are now able to characterize the individual relevance of BOB.1/OBF.1 under immune-pathological conditions and thus to further elucidate the role of BOB.1/OBF.1 in autoimmune processes. Therefore, the aim of the here proposed study is the identification of molecular mechanisms in which the transcriptional co-activator BOB.1/OBF.1 is involved during B and T cell development and differentiation as well as new functions of BOB.1/OBF.1 in those processes under physiological and also immune-pathological conditions.