Krummel K A, Roberts L R, Kawakami M, Glover T W, Smith D I
Department of Laboratory Medicine and Pathology, Mayo Foundation, Rochester, Minnesota 55905, USA.
Genomics. 2000 Oct 1;69(1):37-46. doi: 10.1006/geno.2000.6321.
Fragile sites appear as breaks, gaps, or decondensations on metaphase chromosomes when cells are grown under specific culture conditions. The breaks are nonrandom, appearing in defined, conserved locations throughout the mammalian genome. Common fragile sites, as their name implies, are present in virtually all individuals. With three common fragile sites cloned, their mechanism of expression and the role, if any, they play in human disease are still unclear. We have assembled a BAC contig of >1 Mb across the second most active common fragile site, FRA16D (16q23.2). We fluorescently labeled these BACs and used them as probes on metaphases from aphidicolin-induced lymphocytes and demonstrated that FRA16D decondensation/breakage occurs over a region of at least 1 Mb. Thus, this is the largest common fragile site cloned to date. Microsatellite markers that map within FRA16D show a very high loss in prostate, breast, and ovarian tumors, indicating that loss within this fragile site may be important in the development or progression of these tumors. In addition, a common t(14q32;16q23) translocation is observed in up to 25% of all multiple myelomas (MM). We localized four of four such cloned t(14;16) MM breakpoints within the FRA16D region. This work further demonstrates that the common fragile sites may play an important role in cancer development.
当细胞在特定培养条件下生长时，脆性位点在中期染色体上表现为断裂、间隙或解凝缩。这些断裂是非随机的，出现在整个哺乳动物基因组中确定的、保守的位置。顾名思义，常见脆性位点几乎存在于所有个体中。尽管已经克隆出三个常见脆性位点，但它们的表达机制以及在人类疾病中可能发挥的作用仍不清楚。我们构建了一个跨越第二活跃的常见脆性位点FRA16D（16q23.2）的大于1 Mb的BAC重叠群。我们用荧光标记这些BAC，并将它们用作来自阿非科林诱导的淋巴细胞中期的探针，证明FRA16D的解凝缩/断裂发生在至少1 Mb的区域。因此，这是迄今为止克隆的最大的常见脆性位点。定位在FRA16D内的微卫星标记在前列腺癌、乳腺癌和卵巢癌肿瘤中显示出非常高的缺失率，表明该脆性位点内的缺失可能在这些肿瘤的发生或发展中起重要作用。此外，在所有多发性骨髓瘤（MM）中，高达25%的病例观察到常见的t(14q32;16q23)易位。我们将四个这样克隆的t(14;16) MM断点中的四个定位在FRA16D区域内。这项工作进一步证明常见脆性位点可能在癌症发展中起重要作用。
