Brown Natalie, Finnon Rosemary, Manning Grainne, Bouffler Simon, Badie Christophe
Biological Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 ORQ, UK.
Biological Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 ORQ, UK.
Mutat Res Genet Toxicol Environ Mutagen. 2015 Nov;793:48-54. doi: 10.1016/j.mrgentox.2015.07.012. Epub 2015 Jul 28.
Leukaemia is the prevailing neoplastic disorder of the hematopoietic system. Epidemiological analyses of the survivors of the Japanese atomic bombings show that exposure to ionising radiation (IR) can cause leukaemia. Although a clear association between radiation exposure and leukaemia development is acknowledged, the underlying mechanisms remain incompletely understood. A hemizygous deletion on mouse chromosome 2 (del2) is a common feature in several mouse strains susceptible to radiation-induced acute myeloid leukaemia (rAML). The deletion is an early event detectable 24h after exposure in bone marrow cells. Ultimately, 15-25% of exposed animals develop AML with 80-90% of cases carrying del2. Molecular mapping of leukaemic cell genomes identified a minimal deleted region (MDR) on chromosome 2 (chr2) in which a tumour suppressor gene, Sfpi1 is located, encoding the transcription factor PU.1, essential in haematopoiesis. The remaining copy of Sfpi1 has a point mutation in the coding sequence for the DNA-binding domain of the protein in 70% of rAML, which alters a single CpG sequence in the codon for arginine residue R235. In order to identify chr2 deletions and Sfpi.1/PU.1 loss, we performed array comparative genomic hybridization (aCGH) on a unique panel of 79rAMLs. Using a custom made CGH array specifically designed for mouse chr2, we analysed at unprecedentedly high resolution (1.4M array- 148bp resolution) the size of the MDR in low LET and high-LET induced rAMLs (32 X-ray- and 47 neutron-induced). Sequencing of Sfpi1/PU.1DNA binding domain identified the presence of R235 point mutations, showing no influence of radiation quality on R235 type or frequency. We identified for the first time rAML cases with complex del2 in a subset of neutron-induced AMLs. This study allowed us to re-define the MDR to a much smaller 5.5Mb region (still including Sfpi1/PU.1), identical regardless of radiation quality.
白血病是造血系统中最常见的肿瘤性疾病。对日本原子弹爆炸幸存者的流行病学分析表明，暴露于电离辐射（IR）可导致白血病。尽管辐射暴露与白血病发生之间的明确关联已得到认可，但其潜在机制仍未完全了解。小鼠2号染色体上的半合子缺失（del2）是几种易患辐射诱导急性髓系白血病（rAML）的小鼠品系的共同特征。这种缺失是在骨髓细胞暴露后24小时即可检测到的早期事件。最终，15%至25%的受照射动物会发生AML，其中80%至90%的病例携带del2。白血病细胞基因组的分子图谱确定了2号染色体（chr2）上的一个最小缺失区域（MDR），肿瘤抑制基因Sfpi1位于该区域，它编码转录因子PU.1，这在造血过程中至关重要。在70%的rAML中，Sfpi1的剩余拷贝在该蛋白DNA结合域的编码序列中有一个点突变，该突变改变了精氨酸残基R235密码子中的一个CpG序列。为了鉴定chr2缺失和Sfpi.1/PU.1缺失，我们对一组独特的79例rAML进行了阵列比较基因组杂交（aCGH）。使用专门为小鼠chr2设计的定制CGH阵列，我们以前所未有的高分辨率（1.4M阵列 - 148bp分辨率）分析了低线性能量传递（LET）和高线性能量传递诱导的rAML（32例X射线诱导和47例中子诱导）中MDR的大小。Sfpi1/PU.1 DNA结合域的测序确定了R235点突变的存在，表明辐射质量对R235类型或频率没有影响。我们首次在一部分中子诱导的AML中鉴定出具有复杂del2的rAML病例。这项研究使我们能够将MDR重新定义为一个小得多的5.5Mb区域（仍包括Sfpi1/PU.1），无论辐射质量如何都是相同的。
