FACTORS MODULATING GAMMA GLOBIN GENE EXPRESSION

镰状细胞病伴胎儿血红蛋白持续表达的临床改善方法有待探讨。一种转录因子的基因转移能够逆转成人红细胞中γ -球蛋白到β -球蛋白的转换，这是治疗这种毁灭性疾病的一种方法。与编码珠蛋白基因的顺式序列的转移相比，这种策略的一个优势是可以预期的β /S表达的减少。该项目的长期目标是确定一个或多个可能用于这种基因治疗方法的因素。在目前的供资期间，我们确定了可能满足这一标准的三个因素。首先，我们鉴定了阶段选择蛋白复合物的胎儿和红系成分。在胎儿红细胞生成过程中，这种复合物与基因座控制区向γ启动子的募集有关。在我们的第一个特定目标中提出了该复合体的研究，旨在确定该因子c106在SSP复合体形成中的作用，并确定其在胎儿红细胞中的作用。我们将在一种新的原始和最终的红细胞生成模型中评估该因子激活胎儿血红蛋白表达的能力，这种模型是人类-球蛋白位点和人类红细胞祖细胞的转基因小鼠。最终，如果这些研究证明c106能够重新激活胎儿血红蛋白表达，那么其在镰状红细胞生成NOD/SCID模型和非人灵长类动物中调节γ -珠蛋白基因表达的能力将与项目4和5合作确定。此外，我们还开发了一种新的筛选策略，利用新的化学探针进一步鉴定胎儿珠蛋白调节基因。利用这一策略，正如在特定目标2中提出的工作所概述的那样，我们已经确定了两个因子，HLH蛋白Id2和一种新的CCAAT盒结合蛋白同源物Hap5h。有趣的是，胎儿红细胞中Id2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到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，使我们能够识别进一步的胎儿调节因子。综上所述，这些研究将增强我们对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.