Bao Yonghua, Guo Yongchen, Xiao Shuqi, Zhao Zhihui
College of Animal Science and Veterinary Medicine, Agricultural Division, Jilin University, 5333 of Xi'an Road, Changchun, Jilin 130062, PR China.
Vet Immunol Immunopathol. 2010 Sep 15;137(1-2):64-75. doi: 10.1016/j.vetimm.2010.04.011. Epub 2010 May 18.
The immunoglobulin heavy chain variable region in vertebrates is composed of many genes. However, the gene number and the extent of diversity among the VH gene segments vary with the species. To gain insight into the dog VH repertoire, we analyzed its genome sequence. Eighty VH, six DH and three JH segments were mapped to a 1.28Mb region of the dog chromosome 8. Forty-one of these VH genes were potentially functional, and 39 were pseudogenes. The sequence similarity analysis suggests that the dog IgH locus harbors three VH gene families, VH1 (including 76 members), VH2 (including 3 members) and VH3 (including one member), that are classified into mammalian clan III, I and II, respectively. Subsequently, 111 cDNA positive clones from dog 26 mu, 22 gamma, 23 alpha, 16 delta and 24 epsilon chains containing almost full-length VH, DH and JH segments were selected at random. All of the sequences, except for clone G6, which belonged to the dog VH2 family, originated from the dog VH1 family. The germline segments, VH62 (human VH3-21 homology) and VH44 (human VH3-23 homology), seemed to be preferentially used. Our results suggest that the dog VH repertoire appears to be derived from limited germline gene families, and its diversity may rely on junctional diversity and somatic hypermutation.
脊椎动物的免疫球蛋白重链可变区由许多基因组成。然而，VH基因片段的数量和多样性程度因物种而异。为了深入了解犬类VH基因库，我们分析了其基因组序列。80个VH、6个DH和3个JH片段被定位到犬8号染色体的一个1.28Mb区域。其中41个VH基因可能具有功能，39个为假基因。序列相似性分析表明，犬IgH基因座包含三个VH基因家族，VH1（包括76个成员）、VH2（包括3个成员）和VH3（包括1个成员），分别被归类为哺乳动物第III、I和II族。随后，随机选择了来自犬26μ、22γ,、23α、16δ和24ε链的111个cDNA阳性克隆，这些克隆包含几乎全长的VH、DH和JH片段。除属于犬VH2家族的克隆G6外，所有序列均源自犬VH1家族。种系片段VH62（与人VH3-21同源）和VH44（与人VH3-23同源）似乎被优先使用。我们的结果表明，犬类VH基因库似乎源自有限的种系基因家族，其多样性可能依赖于连接多样性和体细胞超突变。
