Sasso E H, Buckner J H, Suzuki L A
Division of Rheumatology, University of Washington, Seattle 98105, USA.
J Clin Invest. 1995 Sep;96(3):1591-600. doi: 10.1172/JCI118198.
The VH26 germline gene occupies two different loci, due to gene duplication, and is one of the most frequently expressed human immunoglobulin VH genes. This report identifies the alleles of each VH26 locus and describes distinct patterns of VH26 polymorphism in three ethnic groups. Oligonucleotide probes targeting VH26 were used in sequence-specific RFLP analysis of DNA from 72 Caucasians, 52 Asians, 35 American Blacks, and members of six families. The A locus, on a 7.0-kb TaqI band, was detected in 89% of Caucasians, 75% of Asians, and 26% of Blacks (chi2 = P < 0.0005). The B locus, detected on a 5.0-kb band in nearly all subjects, was found to have additional alleles occurring at 6.8 kb in 10% of Asians and 3% of Blacks (chi2 = 7.8, P < 0.02) and at 3.7 kb in 1.4% of Caucasians, 21% of Asians, and (9% of Blacks (chi2 = 13.8, P < 0.001). In Asians, only, the 3.7-kb hybridization band represented a multiple-duplication unit containing three or four gene copies. Duplications of other VH26 alleles, and mull alleles of the B locus, were also seen. An exact VH26 sequence was cloned from the 5.0-kb allele and likely exists in the 7.0- and 6.8-kb alleles. A novel sequence cloned from the 3.7-kb allele differed from VH26 by nine nucleotides and appears to have evolved by gene conversion in CDR2. The total diploid gene dose of the A and B loci ranged from one to as many as six copies of VH26-containing genes, and from zero to as many as six to eight copies of the 3.7-kb allele. We conclude that ethnic differences in polymorphism exist at both VH26 loci. These differences could influence VH26 expression because they involve variations in gene copy number and coding region sequence.
由于基因复制，VH26种系基因占据两个不同的基因座，是人类免疫球蛋白VH基因中最常表达的基因之一。本报告鉴定了每个VH26基因座的等位基因，并描述了三个种族群体中VH26多态性的不同模式。针对VH26的寡核苷酸探针用于对72名高加索人、52名亚洲人、35名美国黑人以及六个家族成员的DNA进行序列特异性RFLP分析。在7.0kb的TaqI条带上检测到的A基因座，在89%的高加索人、75%的亚洲人和26%的黑人中被检测到（卡方检验=P<0.0005）。在几乎所有受试者中，在5.0kb条带上检测到的B基因座，在10%的亚洲人和3%的黑人中，在6.8kb处发现有额外的等位基因（卡方检验=7.8，P<0.02），在1.4%的高加索人、21%的亚洲人和9%的黑人中，在3.7kb处发现有额外的等位基因（卡方检验=13.8，P<0.001）。仅在亚洲人中，3.7kb的杂交条带代表一个包含三个或四个基因拷贝的多重重复单元。还观察到其他VH26等位基因的重复以及B基因座的无效等位基因。从5.0kb等位基因中克隆出了一个精确的VH26序列，并且可能存在于7.0kb和6.8kb等位基因中。从3.7kb等位基因中克隆出的一个新序列与VH26有9个核苷酸的差异，并且似乎是通过CDR2中的基因转换进化而来。A和B基因座的总二倍体基因剂量范围从一个到多达六个含VH26基因的拷贝，以及从零到多达六到八个3.7kb等位基因的拷贝。我们得出结论，VH26两个基因座均存在种族多态性差异。这些差异可能会影响VH26的表达，因为它们涉及基因拷贝数和编码区序列的变化。
