SPECIFIC ALLELIC VARIATION AMONG LINKED HLA CLASS II GENES
SPECIFIC ALLELIC VARIATION AMONG LINKED HLA CLASS II GENES
复制标题
连锁 HLA II 类基因之间的特异性等位基因变异
作者：
A. Amar;S. Holbeck;G. Nepom
位点特异性寡核苷酸已被用作探针来检测 HLA 基因 DQ beta、DQ alpha、DX alpha 和 DO beta 的多态性等位基因。这些基因位于 6 号染色体上的 HLA DR 和 DP 基因之间，该区域经常涉及 HLA 内重组。为了区分这些高度同源的HLA II类基因，我们鉴定了编码区中基因座特异性的序列，并合成了与这些区域相对应的短寡核苷酸探针。我们在凝胶杂交过程中使用这些探针来分析限制性酶消化的基因组 DNA 并将多态性条带分配给特定基因座。 Taq I 消化的 DNA 与 DQ-β 特异性探针杂交可检测每个单倍型的单个条带。该条带的大小与表达的 DQ beta 基因精确对应，并区分血清学定义的 DQ 等位基因，为基因组 DQ 分型提供快速方法。使用对 DX α（DQ 亚区中未表达的 α 基因）特异的寡核苷酸探针进行类似分析，检测到 2 个 DX 等位基因，并与新描述的 DO β 基因特异的寡核苷酸杂交，检测到 DO β 处的 2 个等位基因。 DQ、DX 和 DO 基因之间连锁模式的异质性表明，多个基因间位点的频繁重组事件有助于当今单倍型的产生。在一个具有血清学 HLA 相同兄弟姐妹的家庭中直接发现了一个这样的重组事件，其中基因组分析表明 DR 和 DX 之间存在亲本重组事件映射，这与意外的同种异体反应性相关。
Locus-specific oligonucleotides have been used as probes to detect polymorphic alleles for the HLA genes DQ beta, DQ alpha, DX alpha, and DO beta. These genes lie between the HLA DR and DP genes on chromosome 6, a region frequently implicated in intra-HLA recombination. In order to distinguish among these highly homologous HLA class II genes, we have identified sequences in the coding regions that are locus specific and have synthesized short oligonucleotide probes corresponding to these regions. We have used these probes in a gel hybridization procedure to analyze restriction-enzyme-digested genomic DNA and to assign polymorphic bands to a particular locus. Taq I-digested DNA hybridized with a DQ-beta-specific probe detects a single band per haplotype. The size of this band corresponds precisely to the expressed DQ beta gene and distinguishes among the serologically defined DQ alleles, providing a rapid method for genomic DQ typing. Similar analysis with an oligonucleotide probe specific for DX alpha, the nonexpressed alpha gene in the DQ subregion, detects 2 DX alleles, and hybridization with an oligonucleotide specific for the newly described DO beta gene detects 2 alleles at DO beta. Heterogeneity in linkage patterns among DQ, DX, and DO genes suggests that frequent recombinational events at multiple intergenic sites contributed to the generation of present-day haplotypes. One such recombinational event was identified directly in a family with serologically HLA-identical siblings, in which genomic analysis indicated a parental recombination event mapping between DR and DX, which correlated with unexpected alloreactivity.