ISOLATION OF GENE FOR X-LINKED LYMPHOPROLIFERATION

X连锁淋巴增殖症(XLP)是一种遗传性疾病 由EB病毒(EBV)感染所致的免疫缺陷。宁可 而不是初级接触后的自限性传染性单核细胞增多症 EBV，受影响的男孩发展成EBV转化的不受控制的扩散 B细胞，通常最终导致致命的淋巴瘤。因此，XLP是一种基因 MDS患者和器官中EBV诱导的淋巴瘤模型 移植受者。XLP患者遗传缺陷的性质 是未知的，也没有一致的免疫异常 在EBV感染之前在这些儿童中表现出来。我们建议 通过“定位”分离XLP病基因的实验 克隆“的方法。 XLP基因已被定位到染色体Xq25上的一个遗传座位上，并且 三名无血缘关系的患者存在纯合子生殖系缺失 据报告，在该地点大约有2百万个数据库。男孩谁是 X染色体上这一大片段缺失的纯合子没有临床意义 除XLP外的其他异常，表明没有其他“关键”基因 都存在于该染色体上。我们确认了第一批 在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，并以此为起点建立了 酵母人工染色体(YAC)重叠群跨越缺失。至 确定该区域内的潜在转录，我们正在使用外显子 扩增，一种高度灵敏的技术，用来“捕获”来自 基因组DNA。潜在的外显子将用于筛选cdna文库和 在对YAC重叠群进行排序时也将作为标记有用。候选cDNA 将通过测序、表达的组织分布和 无大染色体XLP患者的基因突变分析 删除。XLP疾病基因的鉴定将使 生化和机能实验的目的是确定它在 EB病毒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.