van Dijk K W, Mortari F, Kirkham P M, Schroeder H W, Milner E C
Department of Pathology, University of Washington, Seattle.
Eur J Immunol. 1993 Apr;23(4):832-9. doi: 10.1002/eji.1830230410.
In this report we describe the analysis and mapping of members of the human immunoglobulin VH7 gene family. VH7 and VH1 gene segments are closely related, with individual gene segments sharing between 78% and 82% sequence identity. Divergence from VH1 gene sequence occurs as an abrupt event at the boundary between framework region (FR) 2 and complementarity-determining region (CDR) 2 and continues through a major portion of FR 3. We used polymerase chain reaction amplification to create a 162-base pair probe spanning the family-specific region of CDR 2 and FR 3 that proved suitable for standard Southern analysis of genomic DNA. The VH7 gene family was found to be a small but discrete VH gene family consisting of five to eight germ-line elements, of which at least three are polymorphic. Four different VH7 gene segments were cloned from the germ line of a single individual, and assigned to specific restriction fragments by sequence-specific hybridization. Two of the four VH7 elements were pseudogenes. The pattern of sequence variation in these and other known pseudogenes suggests that these nonfunctional elements may play a role in the evolution of novel VH families. A combination of one and two-dimensional pulsed field gel electrophoresis was employed to map the chromosomal location of all of these VH7 elements. Individual VH7 gene segments were found to be dispersed over a region of at least 940 kb of DNA, and interspersed with members from other VH gene families. The polymorphism of the VH7 gene segments and their scattered location throughout the VH locus makes them potentially useful markers for mapping and linkage studies.
在本报告中，我们描述了人类免疫球蛋白VH7基因家族成员的分析与定位。VH7和VH1基因片段密切相关，各个基因片段的序列同一性在78%至82%之间。与VH1基因序列的差异在框架区（FR）2和互补决定区（CDR）2之间的边界处作为一个突然事件出现，并贯穿FR 3的大部分区域。我们使用聚合酶链反应扩增来创建一个跨越CDR 2和FR 3家族特异性区域的162个碱基对的探针，该探针被证明适用于基因组DNA的标准Southern分析。发现VH7基因家族是一个小而离散的VH基因家族，由五到八个种系元件组成，其中至少三个是多态性的。从一个个体的种系中克隆出四个不同的VH7基因片段，并通过序列特异性杂交将其定位到特定的限制性片段上。这四个VH7元件中有两个是假基因。这些和其他已知假基因中的序列变异模式表明，这些无功能元件可能在新的VH家族的进化中发挥作用。采用一维和二维脉冲场凝胶电泳相结合的方法来定位所有这些VH7元件的染色体位置。发现各个VH7基因片段分散在至少940 kb的DNA区域内，并与其他VH基因家族的成员交错分布。VH7基因片段的多态性及其在整个VH基因座中的分散位置使其成为用于定位和连锁研究的潜在有用标记。
