家禽MHC结构研究进展

禽主要组织相容性复合体(Major histocompatibility complex,MHC)的结构与禽病防控、禽免疫学、禽类遗传学研究密切相关。文章对鸡、火鸡、鹌鹑、鸭和鹅的MHC结构方面的研究进展进行了综述,表明其有以下共同特点:都有保守的MHC区域,包括MHC I基因和MHC II基因及一些功能未知基因;基因排列简单而紧凑;MHC I基因内含子的长度都比哺乳动物小;鸡、火鸡、鸭和鹅的MHC I基因组序列都有8个外显子和7个内含子,MHC IIβ基因组序列都有6个外显子和5个内含子;鸡、火鸡和鹌鹑的BG基因结构模式相同;都存在微卫星重复单元。但也存在种属差异:鸡的MHC I基因和MHC II基因是双拷贝,而鸭、鹅和鹌鹑有若干个拷贝;BG基因的拷贝数及其外显子数目不同。对主要家禽MHC结构进行分析比较,将有利于对禽病学及禽免疫遗传学的进究。     

灵长类主要组织相容性复合体Ⅰ类基因进化概述

主要组织相容性复合体（MHC）是和免疫反应直接相关的基因群。MHC I类分子的多态性和病原体的多变性相对应,它是个体在重大传染疾病中存活下来的重要依据。在灵长类动物进化过程中,由于分化时间的差异和生存压力的不同,造成了各物种MHC I类基因不同的存在状态,使它们的MHC I 类基因在基因数量和基因功能上有所差异,同时还产生了物种特异性基因。本文描述了灵长类MHC I类基因的总体变化特征,并着重讨论了6个典型MHC I 类基因在各典型灵长类物种中的特点及关联性。     

爬行动物MHC基因研究进展

主要组织相容性复合体(MHC)是有颌脊椎动物中发现的编码免疫球蛋白受体的高度多态的基因群,因其在免疫系统中的重要作用而备受关注。脊椎动物不同支系间MHC的结构和演化差异较大。尽管MHC基因特征在哺乳类、鸟类、两栖类和鱼类中已被较好地描述,但对爬行动物MHC的了解仍较少。鉴于爬行动物对于理解MHC基因的演化占据很重要的系统发育位置,研究其MHC具有重要意义。本文就近年来爬行动物MHC的分子结构、多态性维持机制、功能和主要应用的研究现状进行了系统地回顾和总结,并展望了其研究前景。     

主要组织相容性复合体(MHC)基因的研究概况

主要组织相容性复合体(MHC)因其在免疫方面的重要作用而倍受免疫学家重视．随着研究的不断深入,了解到MHC是一个高度多态的基因群,它广泛分布于各种脊椎动物体内．MHC除了具有免疫功能外,还在其它许多方面起作用．MHC基因的多态性是最受关注的特征,尤其是Ⅱ类基因．根据MHC基因的多态性,可以在遗传、进化、行为、保护及生态等许多方面对其进行研究．就目前的研究情况,在结构、功能及应用等方面对MHC作了介绍．     

恒河猴主要组织相容性复合体（MHC）的多态性研究概述

恒河猴是应用最广泛的非人灵长类实验动物,其MHC基因是一个庞大的与免疫功能密切相关的基因群（也称为Mamu基因）,在进化过程形成了Mamu基因不同的存在状态,使得不同个体的Mamu基因在数量和功能上有所差异,同时有些个体还产生了特异性的MHC基因,它的多态性和免疫反应的复杂性相对应。因此,恒河猴MHC多态性的研究,有助于生物科学的发展及指导以恒河猴为动物模型的各种实验。本文主要阐述了恒河猴Mamu基因的结构和功能,以及部分MHC等位基因与疾病的关系,并简要描述了中国恒河猴特异性的MHC基因。     

直接测序法构建圈养大熊猫MHC遗传档案

主要组织相容性复合体(MHC)基因的遗传参数是濒危动物圈养遗传管理的重要参考依据。本研究通过建立MHC基因分型的直接测序方法,对中国大熊猫保护研究中心圈养的91只大熊猫Ailuropoda melanoleuca进行了3个Ⅰ类MHC基因(Aime-C、Aime-I、Aime-L)和4个Ⅱ类MHC基因(Aime-DQA1、Aime-DQA2、Aime-DQB1、AimeDRB3)的遗传变异分析,发现该圈养种群拥有22条Ⅰ类MHC基因和23条Ⅱ类MHC基因,包括3条新发现的Ⅰ类MHC基因,分别命名为Aime-I*08、Aime-L*08和Aime-L*09。Aime-L*08与已报道的Aime-L*02、Aime-L*09与已报道的Aime-L*04的相似率分别为99.8%(1个碱基差异)和99.6%(2个碱基差异)。直接测序法可直接对长片段的Ⅰ类MHC基因区域进行分型,且仅需掌握PCR扩增技术,不需要掌握聚丙烯酰胺凝胶电泳技术以及银染的显色技术,便于各繁育基地开展大熊猫MHC遗传档案的建立工作。此方法对我国大熊猫圈养种群的遗传管理体系的进一步完善具有重要的应用价值。     

两栖动物MHC基因研究进展

MHC是高度多态的基因群,广泛分布于各种脊椎动物体内。由于MHC基因的多态性,使其在脊椎动物的免疫、遗传、进化、保护等许多方面的研究倍受关注。本文综述了两栖类MHC基因自研究以来国内外有关该基因的研究报道,包括其结构、功能以及在两栖类遗传进化、种群遗传学、免疫遗传学及抗病中的应用,并对研究前景进行了展望。     

犬类MHC复合体Ⅱ类基因研究进展

概述了犬类MHCⅡ类基因的物理结构图谱,对基因的结构、功能及表达、基因分型方法、基因多态性、基因与疾病的关联研究等作了详细的综述,指明了对犬类MHCⅡ类基因的研究利于其抗病育种,对人类自身免疫性疾病和器官移植等方面具有重要现实意义。     

三个地方鸡种MHC B-L BII基因遗传变异与免疫性状的关联分析

旨在研究3个地方鸡品种(汶上芦花鸡、莱芜黑鸡、济宁百日鸡)主要组织相容性复合体(Major Histocompatibility Complex,MHC) B-LBII基因遗传变异与绵羊红细胞(Sheep red blood cell,SRBC)、禽流感(Avian influenza,AI)和新城疫(Newcastle disease,ND)抗体滴度等免疫性状的关系,揭示不同品种间基因变异与免疫性状的相关性.以300只地方品种鸡为材料,运用直接测序和聚合酶链式反应-单链构象多态性(PCR-SSCP)等技术检测MHC B-L BⅡ基因的序列变异.在3个地方鸡品种中分别发现了19～22个核苷酸变异位点,可导致其中16～18个氨基酸的变异.3个地方鸡种MHC B-L BⅡ基因中分别有7～8个(Single nucleotide polymorphism,SNP)位点与部分免疫性状存在不同程度的显著相关性.变异位点G97A和T138A在3个品种中均存在,与SRBC、ND、AI抗体滴度均显著相关(P＜0.05).其中,G97A突变在济宁百日鸡中与ND抗体滴度显著相关(P＜0.05),在莱芜黑鸡中与SRBC抗体滴度显著相关(P＜0.05),在汶上芦花鸡中与H9抗体滴度显著相关(P＜0.05);变异位点T138A在汶上芦花鸡和济宁百日鸡中与H9抗体滴度显著相关(P＜0.05).研究表明3个地方鸡种的MHC B-LBII基因遗传变异与免疫性状存在显著关联.     

家禽主要组织相容性复合体的研究进展

随着家禽基因组计划的开展,对家禽的主要组织相容性复合体（MHC）的研究取得了较大的进展。关于家禽MHC的各部分基因研究正在逐步深入,并且完成了MHC部分测序和染色体定位工作。 本文介绍近些年来对家禽MHC的基因结构和作用、与抗体的作用以及相关的基因组研究所取得的进展。人、小鼠及其他动物的相关研究结果将对家禽MHC研究的发展产生重要的影响。 Abstract:As the development of poultry genome project,it has been acquired many advances in the study of poultry MHC.At present,we have achieved some MHC sequences 、 locations of MHC on chromosome and some MHC gene functions.This article give a detailed introduction about gene structure of poultry MHC and its role in immune reaction、relation with antibody and advances in poultry genome about MHC.With the development of related research,how to use the result of the study more efficiently become more and more important to the poultry MHC study.     

MHC variability, life-traits and parasite diversity of European cyprinid fish

Potential links between fish life history traits, an immune investment as measured by variability of the MHC genes and parasitism were analysed in 14 species of cyprinid fish. The hypothesis of the diversity of MHC genes being driven by high parasite diversity, i.e. species richness, was tested and a potential relationship between the MHC diversity and fish life-history traits including adult mortality rate, fecundity, longevity and maturity was investigated. Molecular techniques (SSCP and sequencing) were applied to analyse the MHC nucleotide diversity of the exons 2 and 3 of DAB genes belonging to the MHC class IIB. The comparative analyses, using phylogenetic independent contrasts, revealed a negative relationship between parasite species richness and adult fish mortality rate. We also found a positive relationship between nucleotide diversity of the exon 2 and parasite species richness. Our results suggest that fish species, of which populations are exposed to high parasite pressure, in terms of high parasite species richness, maintain a high genetic diversity of the exon 2 of the MHC genes (presenting the peptide binding regions), allowing them to decrease their natural mortality rate.     

Selective forces shaping diversity in the class I region of the major histocompatibility complex in dairy cattle

The major histocompatibility complex (MHC) is one of the most diverse regions of the mammalian genome. Diversity in MHC genes is integral to their function in the immune system, and while pathogens play a key role in shaping this diversity, the contribution of other selective forces remains unclear. The controlled breeding of cattle offers an excellent model for the identification and exploration of these forces. We characterized the MHC class I genes present in a sample of Canadian Holstein A.I. bulls and compared the results with those obtained in an earlier study. No evidence for a reduction in MHC diversity over 20 years was observed, but the relative frequency of some haplotypes had changed: the formerly rare A12 (w12B) haplotype had become the most common, together with A15, while A19, which dominated the earlier sample, had significantly reduced in frequency. Only 7% of bulls in the current study were MHC homozygous compared with the 14% expected under Hardy-Weinberg. To identify the selective forces at work, a gene substitution model was used to calculate the effects of MHC on selection traits using estimated breeding values for each bull. Significant associations between MHC and production, disease and fertility traits were identified, suggesting that MHC diversity is not merely shaped by disease in this controlled breeding system. The decrease in a common haplotype, the reduced number of homozygous bulls and the associations with disease and production traits together indicate that MHC diversity in dairy cattle is maintained by heterozygote advantage.     

The porcine Major Histocompatibility Complex and related paralogous regions: a review

The physical alignment of the entire region of the pig major histocompatibility complex (MHC) has been almost completed. In swine, the MHC is called the SLA (swine leukocyte antigen) and most of its class I region has been sequenced. Over one hundred genes have been characterised, including the classical class I and class I-related genes, as well as the class II gene families. These results in swine provide new evidence for the striking conservation during the evolution of a general MHC framework, and are consistent with the location of the class I genes on segments referred to as permissive places within the MHC class I region. Recent results confirm the involvement of the SLA region in numerous quantitative traits.     

Female house sparrows "count on" male genes: experimental evidence for MHC-dependent mate preference in birds

Background  

Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain "good genes" that increase offspring fitness. Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits. Several studies with mammals and fish indicate that the genes of the major histocompatibility complex (MHC) influence olfactory cues and mating preferences, and such preferences confer genetic benefits to offspring. We investigated whether individual MHC diversity (class I) influences mating preferences in house sparrows (Passer domesticus).     

鹿科动物MHC的基因组学、多态性及与性状的相关性

近年来主要组织相容性复合体(MHC)基因已经成为保护遗传学和分子生态学重要的遗传标记.鹿科动物是很多生态系统中的关键物种,也包含很多重要的经济物种和濒危物种.因此,鹿科动物的MHC研究可为种群遗传结构、进化、遗传多样性和种群生存力评估、疾病风险评估、抗病力的定向选育等领域的研究提供新的视角.本文从MHC的基因组结构、多态性,与抗病、抗寄生虫的关系,与鹿角生长的关系等方面,综述了20年来鹿科动物MHC的研究成果,并为今后的研究提出了思路.     

Major histocompatibility complex (MHC) related cDNA probes associated with antibody response in meat-type chickens

The major histocompatibility complex (MHC) region was examined as a set of candidate genes for association between DNA markers and antibody response. Intercross F₂ families of chickens were generated from a cross between high (HC) and low (LC) Escherichia coli _i antibody lines. Restriction fragment length polymorphism (RFLP) analysis was conducted by using three MHC-related cDNA probes: chicken MHC class IV ( B-G ), chicken MHC class I ( B-F ), and human MHC-linked Tap2 . Association between RFLP bands and three antibody response traits ( E. coli , sheep red blood cells and Newcastle disease virus) were determined by two methods: by statistically analyzing each band separately and also by analyzing all bands obtained from the three probes by using multiple regression analysis to account for the multiple comparisons. The MHC class IV probe was the highest in polymorphisms but had the lowest number of bands associated with antibody response. The MHC class I probe yielded 15 polymorphic bands of which four exhibited association with antibody response traits. The Tap2 probe yielded 20 different RFLP bands of which five were associated with antibody production. Some Tap2 bands were associated with multiple antibody response traits. The multiband analysis of the three probes' bands revealed more significant effects than the analysis of each band separately. This study illustrates the efficacy of using multiple MHC region probes as candidate markers for quantitative trait loci (QTLs) controlling antibody response in chickens.     

鸡MHC与传染性疾病遗传抗性的相关性研究进展

鸡是我国主要的家禽品种,抗病分子育种在鸡的疾病尤其是传染病控制中有着重要地位,抗性基因选择是其技术关键。鸡主要组织相容性复合体(MHC)基因具有高度多态性,与多种传染性疾病抗性紧密相关,受到家禽育种专家的高度关注。文章介绍国外有关鸡MHC与传染性疾病抗性的相关性及抗性基因研究进展,并展望其在鸡抗病育种中的应用前景。     

Extremely high MHC class I variation in a population of a long-distance migrant,the Scarlet Rosefinch (<Emphasis Type="Italic">Carpodacus erythrinus</Emphasis>)

Although the number of studies focusing on the major histocompatibility complex (MHC) in non-model vertebrates is increasing, results are often contradictory, and the structure of MHC is still poorly understood in wild species. Here, we describe the structure and diversity of exon 3 of MHC class I in a passerine bird, the Scarlet Rosefinch (Carpodacus erythrinus). Using capillary electrophoresis single-strand conformation polymorphism, we identified 82 different MHC class I variants in one Rosefinch population nesting at one site in the Czech Republic. Thus far, this is the highest intra-populational MHC class I variation observed in birds. We have not found support for ‘minimal essential’ MHC in this species since individuals exhibited between three and nine different exon 3 sequences, indicating that there may be at least five amplified MHC class I genes. By cloning, we obtained and analysed 29 exon sequences and found that all of them could be translated into potentially functional proteins. We also show that strong positive selection appears to be acting mainly, but not only, on previously described antigen-binding sites in MHC class I genes. Furthermore, our results indicate that recombination has played an important role in generating genetic diversity of these genes in the Scarlet Rosefinch; we discuss the significance of this extremely high genetic diversity in light of the life history traits of this species, such as long-distance migration. The sequence data described in this paper are accessible in GenBank data library under accession numbers FJ392762–FJ392790.     

Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations

The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans‐species evolution).