袋獾(袋獾属)非经典MHC I类基因的特征分析

Characterisation of non-classical MHC class I genes in the Tasmanian devil (Sarcophilus harrisii).

作者信息

Cheng Yuanyuan, Belov Katherine

机构信息

Faculty of Veterinary Science, University of Sydney, Office 302, RMC Gunn Building B19, Sydney, NSW, 2006, Australia,

出版信息

Immunogenetics. 2014 Dec;66(12):727-35. doi: 10.1007/s00251-014-0804-3. Epub 2014 Sep 30.

Abstract

The Tasmanian devil (Sarcophilus harrisii) is a carnivorous marsupial that is under threat of extinction due to an unusual transmissible disease called Devil Facial Tumour Disease (DFTD). Previous studies on the classical MHC genes have provided important insights into immune responses in this endangered species; however, so far, very little is known about the non-classical MHC genes of this species, which can also play significant roles in the immune system. Here, we report characterisation of five non-classical class I genes in the Tasmanian devil, including Saha-UD, -UK, -UM, -MR1 and -CD1. Saha-UD has been isolated previously and is known to have low genetic polymorphism, though its categorisation as classical or non-classical gene has remained undetermined. In this study, we observed tissue-specific expression of Saha-UD, suggesting that it is more characteristic of a non-classical gene. Restricted tissue expression patterns were also observed for other genes, with an exception of Saha-MR1 being ubiquitously expressed in all examined tissues. Saha-UK, -UM and -MR1 were found to be genetically monomorphic, while four alleles were found at Saha-CD1 with signs of positive selection detected within the α1 domain. Among the four Saha-CD1 alleles, one predominant allele (Saha-CD1*01) showed a high allele frequency of 0.906 in the Tasmanian devil population, resulting in a low heterozygosity (0.188) at this locus. Alternative splicing takes place in Saha-CD1, giving rise to a full-length transcript and a splice variant lacking intact antigen-binding, β2m-binding, transmembrane and cytoplasmic domains.

摘要

袋獾(袋獾属)是一种肉食性有袋动物,因一种名为袋獾面部肿瘤病(DFTD)的罕见传染病而面临灭绝威胁。先前对经典MHC基因的研究为这种濒危物种的免疫反应提供了重要见解;然而,到目前为止,人们对该物种的非经典MHC基因知之甚少,而这些基因在免疫系统中也可能发挥重要作用。在此,我们报告了袋獾中五个非经典I类基因的特征,包括Saha - UD、 - UK、 - UM、 - MR1和 - CD1。Saha - UD先前已被分离出来,已知其遗传多态性较低,尽管其作为经典基因或非经典基因的分类仍未确定。在本研究中,我们观察到Saha - UD的组织特异性表达,这表明它更具有非经典基因的特征。其他基因也观察到了受限的组织表达模式,除了Saha - MR1在所有检测组织中均普遍表达。发现Saha - UK、 - UM和 - MR1在基因上是单态的,而在Saha - CD1处发现了四个等位基因,在α1结构域内检测到正选择迹象。在四个Saha - CD1等位基因中,一个主要等位基因(Saha - CD1*01)在袋獾种群中的等位基因频率高达0.906,导致该位点的杂合度较低(0.188)。Saha - CD1发生可变剪接,产生一个全长转录本和一个缺乏完整抗原结合、β2m结合、跨膜和细胞质结构域的剪接变体。

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