The identification of the novel causative genes in embryonal rhabdomyosarcoma and the elucidation of the molecular mechanism

横纹肌肉瘤是儿童和年轻人最常见的软组织肿瘤。横纹肌肉瘤可分为两种主要的组织学亚型，腺泡型和胚胎型。在肺泡亚型中，两种复发性染色体易位t（2;13）（q35;q14）及其变体t（1;13）（p36;q14）已被确定为特异性细胞遗传学异常。这些易位分别产生PAX 3-FOX 01和PAX 7-FOX 01融合基因。本研究应用光谱核型分析技术（SKY）对一例胚胎型横纹肌肉瘤进行了复杂染色体易位t（2;8;12）的分析，发现了一个新的易位，涉及PAX 3基因位点的染色体带2 q35。此外，我们确定了新的PAX 3重排荧光原位杂交（FISH）分析。为了鉴定这种情况下位于8 q断裂点上的伴侣基因，我们使用位于8 q上的细菌人工染色体（BAC）探针进行了连续FISH分析。根据加州大学圣克鲁斯（UCSC）基因组浏览器（http：//genome. ucsc。edu）。结果表明，TIF 2基因（8 p11）跨越t（2;8;12）复合体的8 q断裂点。FISH分析显示PAX 3-TIF 2融合蛋白在肿瘤细胞中存在。为了鉴定横纹肌肉瘤中涉及TIF 2基因的其他易位，我们用FISH分析了横纹肌肉瘤细胞系（Rh 2、RD、HKBm、RM 2和Rh 30）。然而，未检测到涉及TIF 2基因的易位。

Rhabdomyosarcoma is the most common soft tissue tumor seen in children and young adults. Rhabdomyosarcoma can be classified into two major histological subtypes, alveolar and embryonal. In the alveolar subtype, two recurrent chromosomal translocations, t(2;13)(q35;q14) and its variant t(1;13)(p36;q14), have been identified as the specific cytogenetic abnormalities. These translocations create the PAX3-FOXO1 and PAX7-F0X01 fusion genes, respectively. In the embryonal subtype, however, no recurrent chromosomal abnormalities have been identified.In this study, we analyzed the complex chromosomal translocation t(2;8;12) in one case with embryonal rhabdomyosarcoma by means of spectral karyotyping (SKY) and identified a novel translocation involving chromosome band 2q35, which is the locus of PAX3 gene. Furthermore, we identified the novel PAX3 rearrangement using fluorescence in situ hybridization (FISH) analysis. To identify the partner gene located on the 8q breakpoint in this case, we performed sequential FISH analyses using bacterial artificial chromosome (BAC) probes located on 8q. The BAC clones (RP11 series) were selected according to the University of California Santa Cruz (UCSC) Genome Browser (http://genome. ucsc. edu). The results suggested that TIF2 gene (8p11) spanned the 8q breakpoint of complex t(2;8;12). Furthermore, FISH analysis showed the PAX3-TIF2 fusion in tumor cells. Unfortunately, we could not determine the molecular structure of the PAX3-TIF2 fusion gene.To identify others translocations involving the TIF2 gene in rhabdomyosarcoma, we analyzed rhabdomyosarcoma cell lines (Rh2, RD, HKBm, RM2, and Rh30) using FISH. However, no translocations involving the TIF2 gene were detected.