Charité, CBF, Medizinische Klinik für Hämatologie, Onkologie, Hindenburgdamm 30, 12200 Berlin, Germany.
DNA Repair (Amst). 2011 Nov 10;10(11):1131-7. doi: 10.1016/j.dnarep.2011.08.010. Epub 2011 Sep 22.
The chromosomal translocation t(9;22)(q34;q22), with expression of the BCR-ABL1 fusion gene is the cytogenetic and molecular hallmark of chronic myeloid leukemia (CML) and a subset of acute lymphoblastic leukemia (ALL). Basically two types of BCR-ABL1 chimeric mRNA transcripts have been observed: (1) e13a2/e14a2 transcripts in CML and ALL, resulting from chromosomal breaks in the major breakpoint cluster region (M-bcr) of the BCR gene and (2) e1a2 transcripts in ALL resulting from breaks in the minor breakpoint cluster region (m-bcr) of the BCR gene. To gain a better understanding of this molecular alteration, we developed a long-distance inverse PCR (LDI PCR) method for M-bcr breakpoint identification in BCR-ABL1-positive cases and were thus able to identify the chromosomal breakpoints within the M-bcr in 62 BCR-ABL1-positive samples. The corresponding reciprocal breakpoints were identified and molecularly characterized in 45 of these cases. In 2 samples, the breaks were located 5' to the ABL1 locus and in one case, the der(9) break was identified on 9q34.13 several hundred kB 3' telomeric to ABL1. The analysis of breaks revealed no significant clustering and no association with repetitive elements (Alu, L1, L2) or recombination signal sequence sites. The established LDI PCR permits fast, relatively easy and unbiased identification of breakpoints in the M-bcr region of BCR and also enables the molecular analysis of more complex translocations with breakpoints outside the ABL1 gene locus or other BCR fusion genes.
9 号染色体和 22 号染色体的易位 t(9;22)(q34;q22)，伴有 BCR-ABL1 融合基因的表达，是慢性髓性白血病（CML）和部分急性淋巴细胞白血病（ALL）的细胞遗传学和分子标志。基本上已经观察到两种类型的 BCR-ABL1 嵌合 mRNA 转录本：（1）在 CML 和 ALL 中出现的 e13a2/e14a2 转录本，是由 BCR 基因的主要断裂簇区（M-bcr）的染色体断裂引起的，（2）在 ALL 中出现的 e1a2 转录本，是由 BCR 基因的次要断裂簇区（m-bcr）的染色体断裂引起的。为了更好地理解这种分子改变，我们开发了一种用于 BCR-ABL1 阳性病例中 M-bcr 断点识别的长距离反向 PCR（LDI-PCR）方法，从而能够在 62 个 BCR-ABL1 阳性样本中识别 M-bcr 内的染色体断点。在其中 45 个病例中，确定了相应的反向断点并进行了分子特征分析。在 2 个样本中，断裂位于 ABL1 基因座的 5'端，在 1 个样本中，9 号染色体的 der(9)断裂位于 ABL1 几个几百 kB 3'端的 9q34.13 上。对断裂的分析显示没有明显的聚类，也与重复元件（Alu、L1、L2）或重组信号序列位点没有关联。建立的 LDI-PCR 允许快速、相对容易和无偏地识别 BCR 的 M-bcr 区域中的断点，并且还能够对断点位于 ABL1 基因座之外或其他 BCR 融合基因之外的更复杂的易位进行分子分析。
