RNA Helicase Mutations in Myelodysplastic Syndrome: New Therapeutic Target

 描述(申请人提供)：MDS包括一组异质性的髓系肿瘤，其特征是发育不良、无效的造血、细胞减少和向SAML的演变。新的技术进步使得对包括MDS在内的白血病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。这一发现导致了一种观点，即靶基因剪接模式的变化在MDS和其他白血病的建立或进展中发挥了重要作用。剪接体机制中的分子缺陷为新的诊断、预后和治疗方式打开了可能性。这一建议的灵感来自我们最近在DDX41基因中发现的相对常见的体细胞突变，该基因编码一种带有DEAD-BOX结构域的RNA解旋酶，参与前mRNA的剪接。位于5q35.3的DDX41基因在MDS中经常缺失。此外，我们还发现了多个DDX41基因有胚系移码突变的家系，这些突变与MDS和AML的易感性有关。这类患者的肿瘤通常结合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DDX41的突变和/或单倍体不足导致特定类型的TSG特定或不同组合的错接，最终剪接体缺陷可能导致类似于直接突变或单倍体基因表达不足所产生的致病后果。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后果。在分子水平上，剪接体突变是“功能改变”导致特定基因错接模式的结果。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。功能的部分丧失 在患者样本中发现的DDX41也表明，在这种情况下，合成致命的药物治疗方法可能是可能的。该提案的目标是了解功能突变丧失、单倍体表达不足和错义突变导致的临床相关性和致病机制，并制定有针对性的治疗原则。我们建议的具体目标包括：1)定义DDX41病变的临床特征。Ii)了解DDX41在前mRNA剪接中的作用，并利用体外和细胞培养系统澄清DDX41突变对解旋酶功能、剪接和白血病发生的影响。Iii)构建小鼠品系，以模拟在人类患者中观察到的基因类型，并监测它们的骨髓疾病发展情况。综上所述，我们的建议基于DDX41种系和体细胞突变的发现，有可能阐明MDS的新致病途径，并建立新的治疗靶点和诊断生物标记物。

 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.