CHARACTERIZATION OF VARIATION OF RECOMBINATION IN THE HUMAN MHC

人类主要组织相容性基因重组的特征 MHC复合体（MHC）的功能可能会导致理解 单倍型多样化的意义。之前，我们确定了 27个HLA-II类基因重组家系的交叉位点分布 使用127个新的多态性标记位于整个类II 地区研究表明，这种现象主要发生在三个区域： HLA-DNA和RING 3之间的45 kb间隔，50 kb间隔 DQB 3和DQB 1之间，以及TAP 2基因的8.8kb片段。我们有 现在开始用单个精子鉴定HLA重组染色体 分型方法，以测量重组的可变性 个体之间的频率和位置。来自单个精子的单倍体DNA 使用随机寡核苷酸引物扩增，并且产物是 在MHC侧翼的两个微卫星标记上分型。初步 筛选鉴定出2,136个精子的49条重组染色体， (2.29 1,705例中有20例（1.58%）来自供体A，20例（1.58%）来自供体B。这两 个体在以下频率上存在显著差异： 重组发生在III类（0.57% vs. 0.08%）和I类 (0.77 0.31%）区域，以及整个4兆碱基对区域 包括MHC（2.97%对1.58%）。进一步的研究将 需要确定这些差异是否是单倍型驱动的。

Characterization of recombination in the human major histocompatibility complex (MHC) may lead to an understanding of the functional significance of haplotype diversification. Previously, we determined the distribution of crossover sites in 27 HLA class II recombinant families using 127 novel polymorphic markers located throughout the class II region. Recombination was shown to occur primarily in three regions: the 45 kilobase (kb)-interval between HLA-DNA and RING3, the 50-kb interval between DQB3 and DQB1, and an 8.8-kb segment of the TAP2 gene. We have now begun to identify HLA recombinant chromosomes using single sperm typing methods in order to measure variability of recombination frequency and location among individuals. Haploid DNA from single sperm is amplified using random oligonuclotide primers, and the products are typed at two microsatellite markers flanking the MHC. A preliminary screen has identified 49 recombinant chromosomes of 2,136 sperm typed (2.29%) from donor A and 20 of 1,705 (1.58%) from donor B. These two individuals differed significantly in the frequency at which recombination occurred in the class III (0.57% vs. 0.08%) and class I (0.77% vs. 0.31%) regions, as well as the entire 4 mebabase- pair region encompassing the MHC (2.97% vs. 1.58%). Further studies will be necessary to determine whether these differences are haplotype driven.