Deletion Mapping of Chromosomes in Malignant Lymphoma and Molecular Cloning of a Putative Novel Tumor Suppressor Gene from the Loci

等位基因缺失被认为是肿瘤抑制基因(TSG)存在的指标。利用分布在所有常染色体上的39个高信息量微卫星标记进行的等位基因研究表明，在B细胞非霍奇金淋巴瘤中，在6p处发现了频繁的杂合性丢失(LOH)。为了确定共同缺失区域(CDR)，我们在6P上利用26个高度多态的微卫星标记进行了精细的缺失定位。最常见的LOH发生在D6S1721，在18个信息性病例中有9个(50%)存在等位基因丢失。在32例患者中，有17例(53%)在6P上至少有一个基因座发生LOH。17例中10例为间质缺失，其LOH图谱显示6p上有两个CDR，一个位于D6S1721~D6S260之间(位于6p23~24)，另一个位于D6S265~D6S291之间(位于6p21)。两个CDR的遗传距离为6 cM，CDKN1A(P21)位于CDR的6p21区间内，但在这32例患者中未发现该基因突变。这些数据提示，这两个基因可能含有与恶性淋巴瘤发病相关的新的TSG基因。我们构建了一个酵母人工染色体(YAC)克隆的重叠群，该克隆跨越了6p23-24处最频繁的CDR。该YAC重叠群可用于该区域的精细物理作图和候选TSG的克隆。

Allelic deletions have been thought to be indicators of the presence of tumor suppressor genes (TSGs). As indicated by this allelotype study using 39 highly informative microsatellite markers distributed among all autosomal chromosomes, frequent loss of heterozygosity (LOH) has been found at 6p in B-cell non-Hodgkin lymphoma. To identify the common deleted regions (CDRs), we performed fine deletion mapping using 26 highly polymorphic microsatellite markers on 6p. The most frequent LOH occurred at D6S1721, where 9 of 18 of the informative cases (50%) had allelic losses. Seventeen of 32 cases (53%) exhibited LOH at least at one locus on 6p. Ten of these 17 cases showed interstitial deletions, and their LOH patterns indicated two CDRs on 6p ; one between D6S1721 and D6S260 (at 6p23-24), the other between D6S265 and D6S291 (at 6p21). The genetic distance of both CDRs was 6 cM.The CDKN1A (p21) is reported to be located within the interval of the CDR at 6p21, but no mutation of the gene was found in these 32 patients. These data suggested that these two loci might harbor novel putative TSGs responsible for the pathogenesis of malignant lymphoma. We have constructed a contig of yeast artificial chromosome (YAC) clones spanning the most frequent CDR at 6p23-24. This YAC contig can be used for fine physical mapping of the region and cloning of the candidate TSGs.