北京鸭含有VHδ基因的TCRδ位点结构、表达及其进化特点

Comprehensive analysis of the additional TCRδ locus in Peking duck

关键词:  北京鸭  VHδ基因  TCRδ位点  进化

Key words:  Peking duck  VHδ gene  TCR δ locus  evolution

摘要:

为分析北京鸭含有VHδ基因的TCRδ位点的结构、表达及进化特点，本研究通过筛选北京鸭基因组DNA的细菌人工染色体（Bacterial artificial chromosome，BAC）文库，并对筛选到的BAC克隆进行全长测序，获得包含北京鸭第二个TCRδ位点的约136 Kb的基因组序列；深入分析北京鸭第二个TCRδ位点基因序列，发现北京鸭第二个TCRδ位点上的VHδ、Dδ和Jδ之间没有内含子序列，已在基因组水平已经完成了VDJ的重组；同线性分析显示该基因位点结构为SPPL2A-VHδ-Dδ-Jδ-Cδ-OR-OR，与鸡的第二个TCRδ位点5'端具有同线性关系；通过Q-PCR得到了北京鸭二个TCR位点上基因的组织特异表达特点；全面分析鸟类第二个TCRδ位点上各基因的进化关系，结果显示所有鸟类的祖先中已出现了第二个TCRδ位点；但在进化过程中不同鸟类Cδ基因经历了基因的丢失或者基因的复制。

Abstract:

To investigate genomic organization,expression and phylogeny of the TCRδ,which including VHδ gene in Peking duck,a Peking duck BAC genomic library was screened and a BAC clone containing the second TCR δ locus was sequenced in this study.The total length of the BAC insert is about 136 Kb.A detailed analysis of the BAC sequence showed there were no introns among VHδ, Dδ and Jδ genes,which suggested that they have recombined on the genomic level.Then a complete genomic structure of the second TCR δ locus in the Peking duck was identified,which is organized in an unusual pattern,SPPL2A-VHδ-Dδ-Jδ-Cδ-OR-OR.Syntenic analysis suggested the second TCR δ locus of Peking duck syntenic with chicken's second TCR δ locus.And the mRNA levels in different tissues are measured by Q-PCR.Phylogenetic analysis shows that all Cδ and VHδ genes from birds are clustered together,indicating that all Cδ genes of birds are derived from a common ancestral gene.The gene is either duplicated or lost in different birds during evolution.In summary,this study would provide insight into the evolution of the second TCR δ in birds and improve our understanding of the duck immune system and the evolution of TCRδ genes in birds.