FACTORS MODULATING GAMMA GLOBIN GENE EXPRESSION

镰状细胞病的临床改善与持续胎儿血红蛋白表达应探讨这种疾病。能够逆转成人红系细胞中γ至β珠蛋白转换的转录因子的基因转移代表了治疗这种破坏性疾病的一种方法。与转移编码珠蛋白基因的顺式序列相比，这种策略的优点是预期的β/S表达的伴随减少。该项目的长期目标是确定一个因素（S），可用于这种方法的基因治疗。在目前的资助期内，我们确定了三个可能符合这一标准的因素。首先，我们已经确定了胎儿和红细胞成分的阶段选择蛋白复合物。该复合物与胎儿红细胞生成过程中基因座控制区向γ启动子的募集有关。在我们的第一个具体目标中提出了该复合物的研究，试图定义该因子c106在SSP复合物形成中的作用，并确定其在胎儿红系细胞中的作用。我们将评估该因子在原始和永久性红细胞生成的新模型中激活胎儿血红蛋白表达的能力，即人β珠蛋白基因座和人红系祖细胞的转基因小鼠。最终，如果这些研究表明，c106是能够重新激活胎儿血红蛋白的表达，其调节γ-珠蛋白基因表达的能力，在一个NOD/SCID模型的镰状红细胞生成和非人类灵长类动物将被确定与项目4和5合作。此外，我们还开发了一种新的筛选策略，以确定进一步胎儿珠蛋白调控基因，利用新的化学探针。通过这种策略，如在具体目标2中提出的工作中所概述的，我们已经鉴定了两种因子，HLH蛋白Id 2和一种新的CCAAT盒结合蛋白同源物Hap 5 h。有趣的是，Id 2在胎儿红系细胞中的强制表达导致γ珠蛋白基因表达的9倍诱导。我们建议进一步表征这些因素，以确定它们在γ-β转换中的作用，以及它们潜在的治疗作用。最后，在具体目标3中，我们描述了具有不同结构的进一步新型化学探针的使用，这些化学探针使我们能够识别进一步的胎儿调节因子。总之，这些研究将提高我们对γ珠蛋白基因表达的分子调控的理解，并可能为镰状细胞病的治疗提供新的治疗策略。

The clinical amelioration in sickle cell disease seen with persistent fetal hemoglobin expression should be explored for this disease. Gene transfer of a transcription factor capable of reversing the gamma to beta globin switch in adult erythroid cells represents one approach to the treatment of this devastating disorder. n advantage of this strategy over the transfer of cis-sequences encoding the globin genes is the concomitant reduction of beta/S expression that would be anticipated. The long-term goal of this project is to identify a factor(s) which may be utilized in this approach to gene therapy. Over the current funding period we have identified three factors which may fulfill this criteria. Firstly, we have identified a fetal and erythroid component of the stage selector protein complex. This complex has been implicated in the recruitment of the locus control region to the gamma promoter during fetal erythropoiesis. This complex has studies proposed in our first specific aim seek to define the role of this factor, c106, in the formation of the SSP complex and determine its role in fetal erythroid cells. We will evaluate the ability of the factor to activate fetal hemoglobin expression in a novel model of primitive and definitive erythropoiesis, mice transgenic for the human beta globin locus and human erythroid progenitors. Ultimately, if these studies demonstrate that c106 is capable of reactivating fetal hemoglobin expression, its ability to modulate gamma-globin gene expression in a NOD/SCID model of sickle erythropoiesis and non-human primates will be determined in collaboration with Projects 4 and 5. In addition, we have also developed a novel screening strategy to identify further fetal globin regulatory genes utilizing novel chemical probes. With this strategy, as outlined in the work proposed in specific aim 2, we have identified two factors, the HLH protein Id2 and a novel CCAAT box binding protein homologue Hap5h. Interestingly, enforced expression of Id2 in fetal erythroid cells results in a 9 fold induction of gamma globin gene expression. We propose to characterize these factors further, to determine their role in the gamma to beta switch, as well as their potential therapeutic role. Finally, in specific aim 3 we describe the use of further novel chemical probes with diverse structures that allow us to identify further fetal regulatory factors. In summary, these studies will enhance our understanding of the molecular regulation of gamma globin gene expression and may provide new therapeutic strategies for the treatment of sickle cell disease.