Animal Genome Research Unit, Agrogenomics Research Center, National Institute of Agrobiological Sciences, 2 Ikenodai, Tsukuba, Ibaraki 305-8602, Japan.
Mol Immunol. 2012 Oct;52(3-4):97-107. doi: 10.1016/j.molimm.2012.05.010. Epub 2012 Jun 4.
The number of immunoglobulin heavy chain (IGH) constant genes (IGHC) varies among mammals. To annotate the porcine IGHC genes, we sequenced the entire IGHC-containing genomic region from a single porcine haplotype. The resulting contiguous sequence included in 5' the IGH diversity (D) gene cluster and in 3' TMEM121, which flank the IGHC cluster in the human genome, suggesting that we had obtained the entire genomic region containing porcine IGHC. This region was about 190-kb long, in good agreement with those of other mammals. The porcine IGHC cluster contained 10 genes, IGHM, IGHD, six IGHG genes, IGHE and IGHA. The porcine IGHG genes formed a cluster between IGHD and IGHE, with IGHG3 considered as the most ancient IGHG gene, located at the beginning of the IGHG cluster. Furthermore, the porcine sequence contained two IGHG5 and two IGHG6 genes, but no IGHG genes for IgG2 and IgG4, suggesting flexibility within the IGHG cluster. We also recorded structural differences in the switch regions of the IGHC genes that may be important in their transcription. This haplotype can serve as a reference for future studies on other haplotypes and for functional analysis of porcine immunoglobulin (IG) isotypes.
免疫球蛋白重链（IGH）恒定基因（IGHC）的数量在哺乳动物中有所不同。为了注释猪的 IGHC 基因，我们从单个猪单倍型中测序了整个包含 IGHC 的基因组区域。所得连续序列在 5'端包含 IGH 多样性（D）基因簇，在 3'端包含 TMEM121，这与人类基因组中 IGHC 簇的侧翼相邻，表明我们已经获得了包含猪 IGHC 的整个基因组区域。该区域约 190kb 长，与其他哺乳动物的长度非常吻合。猪的 IGHC 簇包含 10 个基因，IGHM、IGHD、6 个 IGHG 基因、IGHE 和 IGHA。猪的 IGHG 基因在 IGHD 和 IGHE 之间形成一个簇，IGHG3 被认为是最古老的 IGHG 基因，位于 IGHG 簇的开头。此外，猪序列还包含两个 IGHG5 和两个 IGHG6 基因，但没有 IgG2 和 IgG4 的 IGHG 基因，这表明 IGHG 簇具有灵活性。我们还记录了 IGHC 基因的开关区的结构差异，这些差异可能在其转录中很重要。这种单倍型可以作为未来其他单倍型研究和猪免疫球蛋白（IG）同种型功能分析的参考。
