MOLECULAR GENETIC CHANGES IN LEUKEMIA IN INFANTS

这项工作的目的是更好地理解分子遗传学 婴儿白血病的变化。MLL基因易位的研究 染色体带11q23在大多数情况下都存在，并被认为 主要的改变。移位经常发生在子宫内， 提示产前接触DNA拓扑异构酶II抑制剂 可能是相关的病因因素，因为婴儿白血病类似于 白血病与以DNA拓扑异构酶II为靶点的化疗有关。 或者，基本位点是最常见的自发DNA形式 损伤和碱基位置可能影响DNA拓扑异构酶II的裂解。 宗教均衡。我们假设MLL基因组 易位机制涉及DNA对染色体的破坏 拓扑异构酶II与DNA游离端通过DNA重组 修理。我们已经证明DNA拓扑异构酶II 裂解位点和一些MLL基因组易位断裂点。作为标志 在DNA修复方面，我们已经在 MLL与合作伙伴之间的断点连接和序列相似性 暗示同源末端连接的基因。开始的潜伏期 白血病意味着，除了遗传基因的改变外，二次基因改变 易位可能很重要，但候选基因的方法 对二次变化的调查一直没有定论。虽然 MLL有许多不同的伴侣基因，不同的影响因素 易位伙伴关于MLL基因易位对 完全的白血病发生还没有被评估。我们假设在那里 是次要的变化，这种变化的必要性取决于， 在一定程度上，是关于易位伙伴的。第一个目标使用一个新的 克隆MLL基因组断裂点的方法称为狭长柄变异体聚合酶链式反应， 确定伴侣基因的特征，并检查断点连接。这个 第二个目标是解决易位断点是否 功能性DNA拓扑异构酶II的裂解位点及其作用 关于易位时引入的基本位点的切割 断点。如果第一个假设是正确的，易位 断点应与DNA拓扑异构酶II的裂解位点重合 碱性部位应加强卵裂。第三个目的是使用cdna 利用微阵列技术鉴定白血病的继发性基因改变 涉及不同易位伙伴的MLL基因重排。 如果第二个假设是正确的，那么就会有基因的调节 反映二次更改的表达式，以及 二次变化会因伴侣基因的不同而不同。这项工作将 加深对MLL基因易位病因的认识 并确定婴儿白血病的继发性基因变化。

The objective of this work is to better understand the molecular genetic changes in leukemia in infants. Translocations of the MLL gene at chromosome band 11q23 are present in most cases and are considered primary alterations. The translocations frequently occur in utero, suggesting that prenatal exposures to DNA topoisomerase II inhibitors may be relevant etiologic factors, as leukemias in infants resemble leukemias linked to chemotherapy that targets DNA topoisomerase II. Alternatively, abasic sites are the most common form of spontaneous DNA damage and abasic sites may affect the DNA topoisomerase II cleavage- religation equilibrium. We hypothesize that the MLL genomic translocation mechanism involves chromosomal breakage by DNA topoisomerase II followed by recombination of DNA free ends through DNA repair. We have shown a correspondence between DNA topoisomerase II cleavage sites and some MLL genomic translocation breakpoints. As signs of DNA repair, we have recognized untemplated nucleotides at the breakpoint junctions and sequence similarities between MLL and partner genes that suggest homologous end-joining. Latency to the onset of leukemia has implied that secondary genetic changes in addition to the translocations may be of importance, but the candidate gene approach to investigations of the secondary changes has been inconclusive. Although MLL has many different partner genes, the influence of various translocation partners on sufficiency of MLL gene translocations for full leukemogenesis has not been assessed. We hypothesize that there are secondary changes and that the necessity for such changes depends, in part, on the translocation partner. The first aim uses a new approach called panhandle variant PCR to clone MLL genomic breakpoints, characterize the partner genes, and examine breakpoint junctions. The second aim addresses whether the translocation breakpoints are functional DNA topoisomerse II cleavage sites and examines the effects on cleavage of introduction of abasic sites at the translocation breakpoints. If the first hypothesis is correct, the translocation breakpoints should coincide with DNA topoisomerase II cleavage sites and abasic sites should enhance the cleavage. The third aim uses cDNA microarray technology to identify secondary genetic changes in leukemias with MLL gene rearrangements involving different translocation partners. If the second hypothesis is correct, there will be modulations of gene expression that reflect the secondary changes, and the kinds of secondary changes will vary with the partner gene. This work will increase our understanding of the etiology of MLL gene translocations and identify secondary genetic changes in leukemia in infants.