RNA Helicase Mutations in Myelodysplastic Syndrome: New Therapeutic Target

 描述（由申请方提供）：MDS包括一组异质性髓系肿瘤，其特征为发育不良性无效造血、血细胞减少和演变为sAML。新技术的进步使得对白血病（包括骨髓增生异常综合症）基因组缺陷的分析得到了改进。在新的病变中，我们和其他人已经确定了几个剪接体基因的体细胞突变。这一发现导致了这样的建议，即靶基因剪接模式的改变在MDS和其他白血病的建立或进展中起主要作用。剪接体机制中的分子缺陷为新的诊断、预后和治疗方式开辟了可能。这个建议的灵感来自于我们最近在DDX 41基因中发现的相对常见的体细胞突变，DDX 41基因编码一种RNA解旋酶，其DEAD盒结构域参与前mRNA剪接。位于5q35.3的DDX 41基因在MDS中经常缺失。此外，我们已经确定了多个DDX 41种系移码突变的家族，这些家族与MDS和AML的易感性分离。这类患者的肿瘤通常联合收割机了移码突变和另一个等位基因上的特定错义突变。我们的建议是基于这样的假设，即DDX 41的突变和/或单倍不足导致TSG的特定或不同组合的特定类型的错误剪接，并且最终，剪接体缺陷可能导致与直接突变或单倍不足基因表达所产生的致病后果相似的致病后果。因此，剪接体突变可能是影响特定基因的其他分子缺陷的表型复制结果。在分子水平上，剪接体突变是“功能改变”的结果，导致某些基因的特定错误剪接模式。这些预测在我们对其他剪接因子突变的研究中得到了证实。部分功能丧失 在患者样本中观察到的DDX 41的高浓度也表明，在这种情况下，药物治疗的合成致死方法可能是可能的。该提案的目标是了解功能缺失突变、单倍表达不足和错义突变的临床关联和致病机制，并制定有针对性的治疗原则。我们提案的具体目标包括i）DDX 41病变临床特征的定义。ii）理解DDX 41在前mRNA剪接中的作用，并使用体外和细胞培养系统阐明DDX 41突变对解旋酶功能、剪接和白血病发生的影响。iii）构建模拟人类患者中观察到的基因型的小鼠品系，并监测它们的骨髓疾病的发展。总之，基于DDX 41种系和体细胞突变的发现，我们的建议有可能阐明MDS中新的致病途径，并建立新的治疗靶点和诊断生物标志物。

 DESCRIPTION (provided by applicant): MDS encompasses a heterogeneous group of myeloid neoplasms characterized by dysplastic ineffective hematopoiesis, cytopenias and evolution to sAML. New technological advances allowed for improved analysis of genomic defects in leukemias, including MDS. Among new lesions, we and others have identified somatic mutations of several spliceosomal genes. This discovery has led to the proposal that alterations in the pattern of splicing of target genes play a major role in the establishment or progression of MDS and other leukemias. Molecular defects in the spliceosomal machinery open the potential for new diagnostic, prognostic and therapeutic modalities. This proposal was inspired by our recent identification of relatively common somatic mutations in DDX41 gene coding for an RNA helicase with DEAD-box domain involved in pre-mRNA splicing. The DDX41 gene, located at 5q35.3, is frequently deleted in MDS. Furthermore, we have identified multiple families with germline frameshift mutations in DDX41 that segregate with susceptibility to MDS and AML. Tumors in such patients often combine the frameshift mutation and a specific missense mutation on the other allele. Our proposal is based on the hypothesis that mutations and/or haploinsufficiency of DDX41 leads to specific types of mis-splicing of specific or distinct combinations of TSG and ultimately, that spliceosomal defects may result in pathogenetic consequences similar to those produced by direct mutations or haploinsufficient gene expression. Thus, spliceosomal mutations may phenocopy consequences of other molecular defects affecting specific genes. On the molecular level spliceosomal mutations result of "change of function" leading to a specific missplicing pattern of certain genes. These predictions are being confirmed in our studies of other splicing factor mutations. The partial loss of function of DDX41 seen in patient samples also suggests that a synthetic lethal approach to drug treatment might be possible in such cases. The goals of the proposal are to understand the clinical associations and pathogenic mechanisms consequent to loss of function mutations, haploinsufficient expression and missense mutations and to develop targeted therapeutic principles. The specific aims of our proposal include i) Definition of the clinical features of DDX41 lesions. ii) Understanding the role of DDX41 in pre-mRNA splicing and clarification of the effects of DDX41 mutations on helicase function, splicing and leukemogenesis using in vitro and cell culture systems. iii) Construction of mouse strains that model the genotypes observed in human patients and monitoring them for the development of bone marrow disease. In sum, our proposal, based on the discovery of DDX41 germline and somatic mutations, has the potential to elucidate a new pathogenic pathway in MDS and establish a new therapeutic target and diagnostic biomarker.