ISOLATION OF GENE FOR X-LINKED LYMPHOPROLIFERATION

X连锁淋巴组织增生综合征（XLP）是一种遗传性 EB病毒（EBV）感染特异性免疫缺陷。而 自限性传染性单核细胞增多症 受影响的男孩发展不受控制的EBV转化的增殖， B细胞，通常最终导致致命的淋巴瘤。因此，XLP是一种基因 在MDS患者和器官中观察到的EBV诱导的淋巴瘤模型 移植接受者XLP患者遗传缺陷的性质 是未知的，没有一致的免疫学异常， 这些儿童在感染EBV之前就已经表现出了这种症状。我们提出 旨在通过“定位”分离XLP疾病基因的实验 克隆”的方法。 XLP基因已定位于染色体Xq 25的遗传基因座， 三名不相关的患者， 据报道，在该位点上大约有2兆碱基。的男孩 X染色体上这种大缺失的纯合子没有临床意义。 XLP以外的异常，表明没有其他“关键”基因， 都存在于那个染色体位点上。我们发现了第一个 共同区域内的三个已知基因组标记被删除-在所有三个 XLP患者，并已使用这些作为起点，在建立 酵母人工染色体（YAC）重叠群跨越缺失。到 为了确定该区域内的潜在转录本，我们使用外显子 扩增，一种高度敏感的技术，开发用于“捕获”外显子， 基因组DNA潜在的外显子将用于筛选cDNA文库， 也可用作YAC重叠群排序的标记。候选cDNA 将通过测序、表达的组织分布和 在没有总体染色体异常的XLP患者中进行突变分析 删除。XLP疾病基因的鉴定将允许 生物化学和功能实验，旨在确定其作用， EBV转化的淋巴样细胞的生长控制。

X-linked lymphoproliferative syndrome (XLP) is an inherited immunodeficiency specific to infection by Epstein-Barr virus (EBV). Rather than self-limited infectious mononucleosis following primary exposure to EBV, affected boys develop uncontrolled proliferation of EBV-transformed B cells, often culminating in fatal lymphoma. XLP is therefore a genetic model for the EBV-induced lymphomas seen in MDS patients and in organ transplant recipients. The nature of the inherited defect in XLP patients is unknown, and no consistent immunological abnormalities have been demonstrated in these children prior to EBV infection. We propose experiments aimed at isolating the XLP disease gene by a "positional cloning" approach. The XLP gene has been mapped to a genetic locus at chromosome Xq25, and three unrelated patients with homozygous germline deletions of approximately 2 megabases at that locus have been reported. Boys who are homozygous for this large deletion on the X chromosome have no clinical abnormalities other than XLP, suggesting that no other "critical" genes are present within that chromosomal locus. We identified the first of three known genomic markers within the common region deleted-in all three XLP patients, and have used these as starting points in establishing a yeast artificial chromosome (YAC) contig spanning the deletion. To identify potential transcripts within this region, we are using Exon Amplification, a highly sensitive technique developed to "trap" exons from genomic DNA. Potential exons will be used to screen cDNA libraries and will also be useful as markers in ordering the YAC contig. Candidate cDNAs will be screened by sequencing, tissue distribution of expression, and analysis for mutations in XLP patients who do not have gross chromosomal deletions. The identification of the XLP disease gene will allow biochemical and functional experiments aimed at defining its role in the growth control of EBV-transformed lymphoid cells.