中国恒河猴MHC I型部分等位基因的分析

摘要：目的对中国恒河猴主要组织相容性复合体(MHC)l型部分基因进行携带情况调查与分析。方法采用序 列特异性引物(PCR—SSP)分型方法对华南灵长类动物研究中心繁殖的30只谱系清晰的中国恒河猴(Macaca mulatta)的32个MHC I型分子位点进行检测。结果采用的32对引物中,中国恒河猴可检出携带23个MHC—I等 位基因,但基因携带频率存在很大的差异,由3．57％至82．14％不等。结合遗传谱系分析,判断A1·21和b．2睾05 之间以及B·04和B·30之间可能就是连锁的。结论中国恒河猴携带能控制病毒复制的MHC I型基因位点的 频率较高,其基因携带频率与已发表的印度恒河猴携带频率存在明显差异。本研究为促进中国恒河猴在AIDS研 究中的应用,以及为建立携带特定MHC I基因实验猴小种群提供了依据。     

HBK - SPF 鸭 MHC I 区域微卫星标记分析

摘要: 禽主要组织相容性复合体是一组紧密连锁高度多态的基因群,与免疫反应或敏感性密切相关,鸭 MHC I 区域全长 36. 8 kb,由 TAP1、TAP2 和 5 个 MHC I 拷贝基因( UAA-UEA) 组成。HBK-SPF 鸭是中国农业科学院哈尔滨兽医研究所培育的无特定病原体种鸭,分为 B 和 Q 2 个品系,已封闭繁育了 7 个世代。本文在鸭 MHC I 区域筛选了 4个微卫星位点,通过单链构象多态性分析和聚合酶链式反应直接测序,发现 A 位点具有多态性,为( GT) n 的重复结构,第 6 代 HBK-B 和 HBK-Q 的31 个个体和第 7 代 的140 个个体进行聚合酶链式反应,结果直接测序,在重复结构之前的 108bp 中,发现了 4 种纯合单倍型和 6 种杂合单倍型; B 位点未得到目的产物; C 位点位于 MHC I 拷贝基因UDA 和 UEA 之间,扩增结果与 UAA 和 UBA 之间序列高度同源,无法判断基因型; D 位点表现为单态,为( ATA) 15的固定重复结构。本研究为进一步研究鸭 MHC I 基因结构和建立家系提供了依据。     

野生二粒小麦高分子量谷蛋白亚基等位变异分析

本研究采用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）方法,对从国内外引进的175份野生二粒小麦（Triticum dicoccoides）种质资源高分子量谷蛋白亚基（HMW-GS）Glu1-等位基因组成进行了鉴定和分析.结果表明,175份野生二粒小麦中,Glu-1B位点上的HMW-GS有32种变异类型,比普通面包小麦Glu-1B位点编码的HMW-GS的变异类型丰富得多,其中7＋8和14.1＋15.1亚基分布频率最高（占20.00%）;Glu-1A位点编码的HMW-GS有4种变异类型：1、1^＊、2^＊和Null,一共鉴定了10个新的高分子量亚基.这些新的亚基和等位基因有可能成为面包小麦品质改良的候选基因资源.     

白细胞分化抗原基因多态性与缺血性脑卒中发生与发展的关系

目的探讨白细胞分化抗原基因多态性与缺血性脑卒中发生与发展的关系.方法选取缺血性脑卒中患者404例为观察组,同期体检的同年龄段健康人群398名为对照组.采集空腹外周静脉血,单碱基延伸PCR技术对白细胞分化抗原40基因rs1535045 C/T,rs3765459 C/T,rs4810485 C/T,rsl3040307G/A位点多态性进行分型.结果白细胞分化抗原40基因各位点分布情况显示:rs1535045 C/T位点中CC,CT,TT基因型之间差异具有统计学意义(P0.01); rs3765459 C/T,rs4810485 C/T,rsl3040307 G/A位点各基因型之间差异无统计学意义(P0.05).rs1535045 C/T位点等位基因频率在观察组与对照组间差异具有统计学意义(P0.01);携带T突变型等位基因的缺血性脑卒中发生风险较携带C野生型等位基因明显增加,是携带C野生型的1.846倍.rs3765459 C/T,rs4810485 C/T,rsl3040307 G/A位点等位基因频率在观察组与对照组间差异无统计学意义(P0.05).联合基因型分析显示:观察组携带TCCA,TCCG基因单倍型的比例明显高于对照组,携带CCCG基因单倍型的比例明显低于对照组,差异具有统计学意义(P0.05);携带TCCA,TCCG基因单倍型明显增加缺血性脑卒中的发生风险,携带CCCG基因单倍型明显降低缺血性脑卒中的发生风险.结论白细胞分化抗原40基因rs1535045 C/T位点及TCCA,TCCG,CCCG单倍型与缺血性脑卒中的发生与发展可能存在相关性,其中携带T突变型等位基因可能为缺血性脑卒中的遗传易感基因.     

两种抗应激剂对恒河猴抗热应激作用的试验研究

目的研究两种抗应激剂对恒河猴热应激的影响。方法将6只恒河猴随机分为A,B两组采血做9项血液学及9项血液生化指标测定,A组日粮中每只添加VC300 mg/d和VE50 mg/d;B组日粮中添加0.2%苜草素,饲喂两个月后分别将A、B两组恒河猴放入(32±1)℃,湿度70%猴房内,1 h后采血,测定相应血液学及血液生化指标。结果两组动物血液学各项指标试验前后差异不显著(P>0.05);而血液生化值呈现:A组试验后AST、ALP、LDH分别为(101±23.64)U/L,(623.67±233.12)U/L,(1384.33±807.66)U/L,试验前后差异不显著(P>0.05);B组试验后TP、ALB分别为(83.83±16.32)g/L,(38.53±0.57)g/L;试验前后差异不显著。结论VC和VE在恒河猴抗热应激过程中主要作用于维持血液中AST、ALP、LDH的活性稳定,而苜草素主要作用于维持血液中TP、ALB的稳定,两种添加剂能有效提高恒河猴抗热应激的能力。     

应用微卫星标记对海南和广西恒河猴遗传多样性的研究

目的研究微卫星DNA多态性在海南和广西恒河猴遗传多样性中的应用。方法利用11个微卫星位点,对来自这两个地区的恒河猴进行了遗传检测,并通过POPGEN32软件计算各个微卫星座位的等位基因频率、有效等位基因数目(Ne)、多态信息含量(PIC)和遗传杂合度(H)。结果所选择的11个微卫星位点均存在高度的遗传多态性,H为0.6848~0.8785;PIC为0.5826~0.8345;Ne为3.0000~7.1553。以11个微卫星标记为测度,广西恒河猴的Ne、PIC和H的平均值均高于海南猴,分别为4.2583、0.7090、0.7706(广西恒河猴)和4.2054、0.7025、0.7656(海南恒河猴)。结论这种差别可能与地域来源有关。这些研究为微卫星标记分析恒河猴遗传多样性提供理论基础。     

恒河猴植入位点差异基因筛选及蛋白激酶H11的克隆

采用cap-finder全长cDNA扩增技术和抑制消减杂交(SSH)相结合的方法研究了恒河猴胚胎植入初始时期子宫内膜植入位点与非植入位点的基因表达差异情况.在准确获取妊娠9.5 d恒河猴植入位点和非植入位点子宫内膜后,用SSH建立了植入位点消减cDNA文库,从中随机挑选了1440个克隆,通过点杂交获得了179个在植入位点高表达的克隆,经测序和与基因库(Gen-Bank/EMBL)比对分析,证实其中102个克隆对应于人或恒河猴的52个同源基因,75个克隆对应于人的58个EST,另外2个克隆没有找到对应的同源基因,推测为新的基因.对其中最高频率出现的差异表达基因-蛋白激酶H11,通过cDNA末端快速扩增(RACE)法克隆得到了它的全长cDNA序列.与人的蛋白激酶H11相比,cDNA序列同源性达到94%,所编码的蛋白质序列同源性为83%     

新疆维吾尔族人TNFβ-804基因多态性与乙型肝炎易感性的相关性研究

目的：研究TNF-β基因单核苷酸多态性（SNP）804位点与新疆地区维吾尔族人乙型肝炎之间的关系。方法：用套式PCR（nested PCR）和等位基因特异性PCR（allele一speciicfic PCR,AS-PCR）法,对120例乙肝患者和120例正常对照者TNF-β基因SNP804多态性位点进行基因分型。结果：SNP804多态性位点C/C基因型和C/A＋AA基因型频率在病例组为77%和23%,正常对照组为88%和12%,两组间基因型和等位基因频率分布差异有显著性（p〈0.05）。结论：TNF-β804多态性位点与新疆维吾尔族人乙肝有明显相关性。     

Calpain 10基因与新疆维吾尔族2型糖尿病遗传易感性研究

研究Calpain 10基因单核苷酸多态性（SNP）43G-A和63C-T两个位点与新疆地区维吾尔族人群2型糖尿病（Type 2 diabetes mellitus,T2DM）之间的关系。采用1∶1病例——对照研究方法,以聚合酶链式反应——限制性内切酶长度多态性（PCR-RFLP）技术,对120例T2DM患者和120例正常对照者Calpain 10基因SNP43、SNP63多态性位点进行基因分型。SNP43多态性位点的基因型和等位基因频率在病例组和正常对照组中的分布存在差异,T2DM组中GG基因型和等位基因频率均低于对照组,但是A等位基因频率高于对照组,差异有统计学意义（P〈0.005）;SNP63多态性位点的基因型频率和等位基因频率在病例组和正常对照组中的分布无显著差异,（P〉0.005）。结果表明：（1）Calpain 10基因SNP43多态性位点与新疆地区维吾尔族人群T2DM有明显相关性;（2）SNP63多态性位点与新疆地区维吾尔族人群T2DM无明显相关性。     

广东地区感染养殖罗非鱼的无乳链球菌分子分型研究

以广东省内5个罗非鱼Oreochromis niloticus主要养殖区内分离的无乳链球菌Streptococcus agalactiae为研究目标,通过毒力基因PCR检测、多位点序列分型、脉冲场凝胶电泳技术研究广东地区感染罗非鱼的无乳链球菌分子特征。结果发现170株分离无乳链球菌中毒力基因的携带率介于60.59%~100%之间,毒力基因携带形成10个谱系,dltR-bca-sod A-spb1-cfb-bac(38.24%,65/170),dltr-bca-sod A-spb1-bac(23.53%,40/170)和dltr-bca-sod A-spb1-cfb-bac-scp B(22,35%,38/170)为主要的谱系,dltr-bca-sod A-spb1-bac-scpb(8.24%,14/170)和dltr-bca-sod A-spb1(4.71%,8/170)次之。多位点序列分型研究证实170株菌在7个位点均为单一的等位基因,为adh P(10),phe S(1),atr(2),gln A(1),sdh A(3),glc K(2),tkt(2),序列型为ST7型。146株菌脉冲场凝胶电泳结果表明146株菌分为6个簇(A-D,F,G),相似性介于86%~100%之间。A(18),B(16),C(103),D(7)为主要的遗传簇,占菌株数的98.63%(144/146)。基因簇A,C在4个采样区均有发现;基因簇B分布在吴川、茂名和阳江;基因簇D分布在茂名、珠海和阳江;基因簇F和G分别来自茂名和珠海。在A-D遗传簇中均有发现来自不同地区的菌株呈现100%的相似性,为同一克隆株。结果表明广东省主要罗非鱼养殖区内感染链球菌携带毒力基因比率高,序列型均为高致病的ST7型别,不同地区间具有相同的PFGE型别,不同地区间交叉传播感染的可能高。     

Localization of type 1 diabetes susceptibility to the MHC class I genes HLA-B and HLA-A

The major histocompatibility complex (MHC) on chromosome 6 is associated with susceptibility to more common diseases than any other region of the human genome, including almost all disorders classified as autoimmune. In type 1 diabetes the major genetic susceptibility determinants have been mapped to the MHC class II genes HLA-DQB1 and HLA-DRB1 (refs 1-3), but these genes cannot completely explain the association between type 1 diabetes and the MHC region. Owing to the region's extreme gene density, the multiplicity of disease-associated alleles, strong associations between alleles, limited genotyping capability, and inadequate statistical approaches and sample sizes, which, and how many, loci within the MHC determine susceptibility remains unclear. Here, in several large type 1 diabetes data sets, we analyse a combined total of 1,729 polymorphisms, and apply statistical methods-recursive partitioning and regression-to pinpoint disease susceptibility to the MHC class I genes HLA-B and HLA-A (risk ratios >1.5; P(combined) = 2.01 x 10(-19) and 2.35 x 10(-13), respectively) in addition to the established associations of the MHC class II genes. Other loci with smaller and/or rarer effects might also be involved, but to find these, future searches must take into account both the HLA class II and class I genes and use even larger samples. Taken together with previous studies, we conclude that MHC-class-I-mediated events, principally involving HLA-B*39, contribute to the aetiology of type 1 diabetes.     

MHC polymorphism pre-dating speciation

Two features distinguish the polymorphism of the major histocompatibility complex (MHC) loci from that of other loci: its high diversity and the large genetic distance between MHC alleles. More than 100 alleles exist in natural populations in the mouse at each of the functional class I and class II alleles, all alleles occurring at frequencies that cannot be explained by recurrent mutations. Some of the alleles differ by approximately 70 nucleotides in the coding region alone and some of the products of the allelic genes differ by more than 50 amino acids. It has generally been assumed that these differences accumulated after species inception. Here, we present evidence for an alternative explanation of the origin of MHC polymorphism: a large part of the MHC polymorphism pre-dates speciation and is passed on from species to species. We describe allelic differences that must have arisen before the separation of mice and rats from a common ancestor more than 10 million years ago.     

MHC antigens in urine as olfactory recognition cues

The classical class I antigens of the major histocompatibility complex (MHC) are cell-surface glycoproteins which were originally discovered because they cause rapid rejection of cells or tissues grafted between unrelated individuals. These molecules are encoded by the K, D and L loci of the mouse MHC (and analogous loci in other species) which show extreme species polymorphism and a large number of alleles. In an outbreeding population 3.6 X 10(9) unique MHC class I phenotypes can be encoded by the 100 alleles at each of the K and D loci and the 6 alleles at the L locus. This level of polymorphism ensures that the cells and tissues of each unrelated individual are uniquely identified by their class I membrane-bound antigens. Like other membrane bound proteins, these class I molecules are anchored in the lipid bilayer by a hydrophobic domain encoded by exon 5. However, there have been reports of the occurrence of classical class I molecules in true solution in the blood of humans, mice, and rats. We report here that classical polymorphic class I molecules in normal rats are constitutively excreted in the urine and that untrained rats can distinguish the smell of urine samples taken from normal donors that differ only at the class I MHC locus and therefore excrete different allelomorphs of class I molecules in their urine.     

Isolation and characterization of class I MHC genes in the giant panda (Ailuropoda melanoleuca)

Artificial breeding is an important project to protect,recover and reintroduce endangered species.Knowledge of the population’s genetic diversity at functional loci is important for the establishment of effective captive breeding programs.The major histocompatibility complex(MHC) genes are ideal candidate genetic markers to inform planned breeding,due to their high levels of polymorphism and importance in the main immune coding region of the vertebrate genome.In this study,we constructed BAC-based contigs and isolated six functional MHC class Ⅰ genes from the giant panda(Ailuropoda melanoleuca),which we designated Aime-C,Aime-F,Aime-I,Aime-K,Aime-L and Aime-1906.Analyses of the tissue expression patterns and full-length cDNA sequences of these class I genes revealed that Aime-C,-F,-I and-L could be considered classical class Ⅰ loci,due to their extensive expression patterns and normal exonic structures.In contrast,Aime-K and-1906 appeared to be nonclassical genes based on their tissue-specific expression patterns and the presence of an abnormal exon 7 in both genes.We established techniques for genotyping exons 2 and 3 of the classical loci using locus-specific single strand conformation polymorphism(SSCP) and sequence analysis.In the Chengdu captive population,we identified one monomorphic locus(Aime-F) and three polymorphic loci with different numbers of alleles(4/4/4 exon 2 alleles at Aime-C/I/L and 6/5/5 exon 3 alleles at Aime-C/I/L).The distributions of the Aime-C,-I and-L alleles among members of different families were in good agreement with the known pedigree relationships,suggesting that the genotyping results are reliable.Therefore,the MHC-I genotyping techniques established in this study may provide a powerful tool for the future design of scientific breeding or release/reintroduction programs.     

Correlation between a DNA restriction fragment length polymorphism and C4A6 protein

The fourth component of complement (C4) in man, is coded for by two separate but closely linked loci (C4A and C4B) within the major histocompatibility region (MHC), on the short arm of chromosome 6. Like class I and II loci of this region, the C4 genes are highly polymorphic with more than 30 alleles, including null alleles, assigned to the two loci. This extensive polymorphism, based mainly on electrophoretic mobility, provides a useful marker for studies of disease susceptibility. Several disorders, including systemic lupus erythematosus and type I diabetes, show associations with C4 phenotypes. We have used the technique of Southern with a C4 specific probe to examine the genomic DNA of individuals typed for C4 by protein electrophoresis. We have identified 10.7 and 3.8 kilobase (kb) BglII restriction fragments in each of 9 unrelated individuals with a C4A6 allele, and in none of 22 unrelated individuals in whom this allele was not expressed. This clear correlation of restriction fragment length polymorphism with C4 phenotype provides a precise basis for analysis of C4 polymorphism. It is likely to be of value in clinical investigations of autoimmune disease.     

MHC polymorphism and disease-resistance to Edwardsiella tarda in six turbot (Scophthalmus maximus) families

This study examined genetic variation in the major histocompatibility complex(MHC) Class II B gene in turbot(Scophthalmus maximus) by virulent bacterial pathogen challenge.One hundred fry from each of six families were infected with Edwardsiella tarda by intraperitoneal injection.Family mortality ranged from 28.0% to 83.3%.Complete exon 2 and intron 1 sequences of MHC Class II B genes were amplified from five survivor and five non-survivor individuals per family using the clone-sequence method.Thirty-seven sequences from 60 individuals revealed 37 different alleles,25 of which were unique to this study.The 25 unique alleles belonged to 16 major allele types.Nine alleles were used to examine the association between alleles and resistance/susceptibility to disease.Five alleles were present in an individual,suggesting a minimum of three loci or copies of the turbot MHC Class II B gene.The rate of non-synonymous substitution(d N) was 2.30 and 1.58 times higher than synonymous substitution(d S) in the peptide-binding regions(PBR) and non-PBR in whole families,respectively,which suggested balancing selection on exon 2 of the MHC Class II B gene in turbot.One allele,Scma-DBB1*02,was significantly more prevalent in survivor stock than in non-survivor stock(P=0.001).Therefore,this allele might be associated with resistance to bacteria.A second allele,Scma-DBB1*10,was significantly more prevalent in non-survivor stock(P=0.021),and is likely associated with susceptibility to bacteria.     

Physical association between MHC class I molecules and immunogenic peptides

Antigenic peptides are presented to T lymphocytes by major histocompatibility complex (MHC) molecules. The binding of peptides to MHC class II molecules has been demonstrated directly, and is found to correlate with the ability of specific class II alleles to restrict the T-cell response to specific peptides. By comparison, a direct demonstration of a physical association between antigenic peptides and MHC class I molecules has proved difficult. A recent report shows that it is possible, however, and the three-dimensional structure of a class I MHC molecule illustrates the site where such binding must occur. Here we describe a simple assay which measures the binding of radiolabelled MHC class I molecules to peptides bound to a solid phase support. We find that class I molecules bind specifically to peptides known to be antigenic for class I-restricted cytotoxic T lymphocytes. Peptides which are recognized by cytotoxic T lymphocytes bind not only to the restricting MHC class I molecule but also to other class I molecules. Our results suggest that quantitative differences in the peptide/MHC class I interaction may influence the-pattern of MHC restriction observed in vivo.     

The origin of MHC class II gene polymorphism within the genus Mus

The I region of the major histocompatibility complex (MHC) of the mouse (H-2) contains a tightly-linked cluster of highly polymorphic genes (class II MHC genes) which control immune responsiveness. Speculation on the origin of this polymorphism, which is believed to be essential for the function of the class II proteins in immune responses to disease, has given rise to two hypotheses. The first is that hypermutational mechanisms (gene conversion or segmental exchange) promote the rapid generation of diversity in MHC genes. The alternative is that polymorphism has arisen from the steady accumulation of mutations over long evolutionary periods, and multiple specific alleles have survived speciation (trans-species evolution). We have looked for evidence of 'segmental exchange' and/or 'trans-species evolution' in the class II genes of the genus Mus by molecular genetic analysis of I-A beta alleles. The results indicate that greater than 90% (28 out of 31) of the alleles examined can be organized into two evolutionary groups both on the basis of restriction site polymorphisms and by the presence or absence of a short interspersed nucleotide element (SINE). Using this SINE sequence as an evolutionary tag, we demonstrate that I-A beta alleles in these two evolutionary groups diverged at least three million years ago and have survived the speciation events leading to several modern Mus species. Nucleotide sequence comparisons of eight Mus m. domesticus I-A beta alleles representing all three evolutionary groups indicate that most of the divergence in exon sequences is due to the steady accumulation of mutations that are maintained independently in the different alleles. But segmental exchanges between alleles from different evolutionary groups have also played a role in the diversification of beta 1 exons.     

Pattern of nucleotide substitution at major histocompatibility complex class I loci reveals overdominant selection

The major histocompatibility complex (MHC) loci are known to be highly polymorphic in humans, mice and certain other mammals, with heterozygosity as high as 80-90% (ref. 1). Four different hypotheses have been proposed to explain this high degree of polymorphism: (1) a high mutation rate, (2) gene conversion or interlocus genetic exchange, (3) over dominant selection and (4) frequency-dependent selection. In an attempt to establish which of these hypotheses is correct, we examined the pattern of nucleotide substitution between polymorphic alleles in the region of the antigen recognition site (ARS) and other regions of human and mouse class I MHC genes. The results indicate that in ARS the rate of nonsynonymous (amino acid altering) substitution is significantly higher than that of synonymous substitution in both humans and mice, whereas in other regions the reverse is true. This observation, together with a theoretical study and other considerations, supports the hypothesis of overdominant selection (heterozygote advantage).     

Structural and serological similarity of MHC-linked LMP and proteasome (multicatalytic proteinase) complexes

Major histocompatibility complex (MHC) class I molecules associate with peptides derived from endogenously synthesized antigens. Cytotoxic T-lymphocytes can thus scan class I molecules and bound peptide on the surface of cells for foreign antigenic determinants. Recent evidence demonstrates that the products of trans-acting, non-class I genes in the class II region of the MHC are required in the class I antigen-processing pathway. There are genes (called HAM1 and HAM2 in the mouse) in this region that encode proteins postulated to be involved in the transport of peptide fragments into the endoplasmic reticulum for association with newly synthesized class I molecules. But, the mechanism by which such peptide fragments are produced remains a mystery. At least two genes encoding subunits of the low-molecular mass polypeptide (LMP) complex are tightly linked to the HAM1 and HAM2 genes. We show that the LMP complex is closely related to the proteasome (multicatalytic proteinase complex), an intracellular protein complex that has multiple proteolytic activities. We speculate that the LMP complex may have a role in MHC class I antigen processing, and therefore that the MHC contains a cluster of genes required for distinct functions in the antigen processing pathway.