中国地区汉族人类血小板抗原基因多态性研究

为探讨中国汉族人群的人类血小板特异性抗原(human platelet antigens,HPA)的基因多态性特点并对南北方汉族人群进行比较,本研究合并了24个地区的28篇HPA基因多态性调查文献中HPA-1、HPA-2、HPA-3、HPA-4、HPA-5、HPA-6和HPA-15的基因分型数据,利用统计学方法及相关软件进行整理,并对整理后数据进行对比分析。结果显示HPA-1、HPA-2、HPA-3、HPA-4、HPA-5和HPA-6位点的a、b基因频率差距很大且bb基因型频率接近于0,而HPA-3和HPA-15位点的a、b基因频率差距不大。南北方汉族人群的比较中,HPA-1和HPA-5的基因分型有所差异,而HPA-2的基因型频数分布差异有统计学意义(p0.05)。此结果旨在获取人类血小板抗原基因多态性的特点并提供建立人类血小板抗原数据库的相关资料,对临床输血的指导具有重要意义。     

人类血小板抗原1～6系统同步基因分型的研究

为研究采用PCR—SSP技术,建立可靠的人类血小板抗原HPA-1,2,3,4,5,6系统的同步基因分型方法,并以所建立的方法研究血小板抗原。设计合成18条序列特异性引物,探索最佳退火温度,通过调整引物浓度、Mg2＋离子浓度,使HPA-1~6系统等位基因在同一条件下进行同步扩增和扩增产物在同一凝胶中进行同步电泳。引物的特异性和灵敏度采用基因型已知的质控DNA进行验证。应用此方法,对2000年度国际输血协会（ISBT）第十届血小板基因定型与血清学工作组送检的15份考核样本（其中血样2份,DNA样本13份）进行了基因分型。用此方法检测质控DNA,结果与已知的HPA基因型完全相符;15份第十届血小板基因定型与血清学工作组的考核样本的检测结果,与ISBT公布的结果完全相同,准确率达100%。Abstract: To set up the simultaneous genotyping of human platelet antigens of 1,2,3,4,5,6 system by PCR—SSP assay and use the genotyping method for the study of platelet antigens. In this study, 18 sequence-specific primers were designed and synthesized. The annealing temperature for all sequence-specific primer pair, the concentration of each primer pair and the concentration of Mg2+ were adjusted to the optimum so that HPA-1 to 6 systems could be amplified simultaneously under the same PCR cycling parameters. The electrophoresis of PCR products was conducted simultaneously on the same agarose gel. Control DNA samples that genotypes known were used to confirm the sensitivity and specificity of each sequence-specific primer. 15 coded samples (including 2 blood samples and 13 DNA samples) distributed by 10TH Platelet Genotyping and Serology Workshop of the International Society of Blood Transfusion (ISBT) were typed for HPA-1 to 6 systems by this method. A concordance rate of 100 percent was observed between the results of control DNA samples typed by our PCR—SSP assay and the data of known specificity of control DNA. The results of 15 coded samples tested by our method agreed well with the results provided by ISBT report.     

HIV-1 gp160多表位嵌合基因的构建及表达蛋白的免疫原性分析

HIV感染引起的AIDS已经成为严重影响人类健康和社会发展的全球性疾病。酶联免疫吸附试验和免疫印迹检验组合则被认为是HIV检测的“金标准”。因此本实验构建gp160的抗原多表位融合基因及在原核系统的高表达, 为HIV抗体测定提供特异、价廉的抗原。选定HIV-1 gp160基因中三个片段包含较多抗原表位的区域, 设计带有酶切位点的引物,用PCR的方法从HIV-1HXB2全基因扩增编码这三个片段的基因序列,通过质粒提取、酶切、测序方法鉴定基因片段的正确性, SDS-PAGE和Western Blot测定融合蛋白的抗原特异性。构建的HIV-1 gp160多表位嵌合基因的原核表达质粒,酶切和测序结果表明基因序列正确,基因全长969bp。在大肠杆菌BL21(DE3) 中高效表达的重组蛋白分子量为37kDa,以包涵体的形式存在。应用western blot测定10例正常人和12例HIV/AIDS病人血浆显示HIV-1 gp160多表位融合蛋白具有良好的抗原特异性。成功构建了高表达 HIV-1 gp160多表位蛋白的原核表达系统,纯化的融合蛋白有较强的抗原特异性。     

185例儿童急性白血病流式细胞术免疫分型研究

目的:探讨儿童急性白血病流式细胞术免疫分型的意义。方法:采用流式细胞术三色荧光标记技术和CD45/SSC双参数散点图设门,检测185例儿童急性白血病的免疫表型,对抗原表达情况进行分析。结果:流式细胞术免疫分型和FAB分型的符合率为89.19%。185例儿童急性白血病中,ALL为121例,占AL的65.41%,B-ALL为113例,主要表达B系的CD19(99.12%)、CD22(98.13%)、CD79a(96.19%)、CD10(86.73%)。T-ALL占8例;主要表达CD5(100%)、CD7(100%)、cCD3(100%)、CD8(87.5%)。AML为47例,占25.41%,主要表达CD33(93.62%)、CD15(78.72%)、CD64(76.6%)、MPO(76.6%)、CD13(74.47%)。在B-ALL,AML,T-ALL中,敏感性最高的抗体分别是CD19,CD33,CD5和CD7,特异性最强的抗体分别是CD79a,MPO,cCD3。AMLL为17例,占9.19%,其中B/M为9例,T/B为5例,T/M为3例。My十-ALL为54例,占ALL的44.63%,表达的髓系抗原为CD13、CD15、CD33、CD64。Ly+-AML为18例,占AML的38.30%,表达的淋系抗原为CD19、CD4、CD7。系列非相关抗原CD34的表达率为67.57%,HLA-DR的表达率为85.41%,CD38的表达率为80.59%,TdT的表达率为62.59%。结论:流式细胞术免疫分型在白血病分型中起重要作用,是FAB分型的补充和修正,提高了儿童急性白血病诊断的准确率有必要进一步加强流式细胞术免疫分型的标准化工作。     

沙门菌鞭毛抗原及其多样性研究进展

沙门菌鞭毛蛋白具有抗原性。鞭毛分型抗原有多种,抗原特异性取决于氨基酸序列和种类的不同,抗原表位在鞭毛蛋白二级结构的可变区部位,在分子水平上抗原决定区位于鞭毛基因中间可变区中。利用分型抗原特异性建立起来的免疫学检测被广泛应用。沙门菌属特异性共同抗原具有属特异性,广泛分布于沙门菌全属。共同抗原具有序列保守性和构像稳定性,在沙门菌属内同源性高,ELISA试验表明此抗原免疫原性较好,利用此抗原属特异性建立起免疫学检测沙门菌属已得到应用。     

基于纳米抗体CDR3区抗原表位展示制备生存素抗体及其鉴定

目的:通过纳米抗体CDR3区展示生存素N端表位的方式,探索纳米抗体在抗原表位展示中的作用。方法:通过基因合成方法将生存素N端起始表位(氨基酸序列1~15)插入纳米抗体CDR3区,再构建到原核表达载体pET24a中,IPTG诱导表达,用带His标签的填料纯化,获得高纯度的目的蛋白,免疫雌性BALB/c小鼠,间接ELISA检测5次免疫后的效价,用抗原偶联纯化介质纯化免疫多抗,Western印迹检测多抗特异性。结果:IPTG诱导后,目的蛋白主要以包涵体形式存在,亲和层析获得纯度大于96%的目的蛋白,包涵体经复性后免疫小鼠,效价可达1∶512000,West?ern印迹特异性检测显示免疫多抗能够特异性结合生存素。结论:纳米抗体CDR3区生存素抗原N端表位展示的方法可用于抗生存素抗体的制备,并为今后纳米抗体表位展示相关研究奠定基础。     

急性B淋巴细胞白血病儿童化疗后微小残留病灶免疫表型改变的分析

目的:分析儿童急性B淋巴细胞白血病(B-cell acute lymphoblastic leukemia,B-ALL)化疗过程中首次微小残留病灶(minimal residual disease,MRD)免疫表型的变化规律及特点,为临床诊断及后续微小残留病的监测提供依据。方法:回顾性分析我院2013年1月至2018年4月收治的393例B-ALL患儿的免疫分型结果及诱导化疗第15天首次MRD数据。结果:(1)在393例白血病中,B-ALL相关特征性免疫表型的出现频率为:CD19+/CD10+/34+64.4%;CD19+/CD10+/34部分表达,15.5%;CD19+/CD34+/CD20+,58.5%;CD19+/CD10+/CD13+,13.2%;CD19+/CD10+/CD33+,5.9%;CD19+/CD10+/CD117+,0.7%;CD19+/CD10+/CD123+,50.1%;CD19+/CD10-/34±,5.9%;CD19+/CD10-/CD20-,2.5%;CD34bright,12.2%;(2)共有285例首次MRD检测结果呈阳性,有181例(63.5%)MRD检测结果至少有1个抗原荧光强度发生改变,其中出现一个抗原强度变化的为83例(29.1%),2个抗原荧光强度变化的为57例(20.0%),3个抗原荧光强度变化为31例(10.9%),4个及4个以上抗原荧光强度变化为10例(3.5%)。抗原荧光强度变化频率最高的依次为CD45、CD34、CD20;(3)共有7例患儿复发,复发时行免疫分型检测,其中4例与初发时有抗原荧光强度变化。结论:(1)儿童B-ALL远高于其他白血病类型,且具有独特的相关特征性免疫表型。初发B-ALL免疫分型结果不仅可完善白血病MICM分型,更是化疗后MRD监测的线索及客观依据;(2)在儿童B-ALL化疗过程中,免疫表型极有可能会发生变化,在后续的微小残留病灶检测过程中应注意对变化抗原的判断和追踪。     

利用HPA-1～3,5和15系统多态性估算中外不同人群遗传距离

依据血小板同种抗原5个系统的遗传多态性, 采用聚合酶链反应序列特异性引物技术, 对1 000名中国汉族无关献血者HPA-1~3, 5和15系统进行基因分型, 计算基因频率。使用DISPAN软件及PHYLIP软件计算不同群体间遗传距离并绘制系统树。系统树显示, 亚洲人群先与欧洲人群相聚, 之后再与非洲人群相聚, 非洲人群位于系统发生树的最顶部; 印度人群处于亚洲人群与欧洲人群之间; 南美洲巴西白人与欧洲人群聚在一起; 大洋洲的波利尼西亚人与亚洲人群聚在一起。此研究从一个侧面证明了人类“非洲起源说”, 印证亚洲人群由南亚向东南亚再向东亚迁徙的路线, 并推断出欧洲人群由南欧向北欧、西欧迁徙的线路。HPA能有效估算不同人群间遗传距离, 分析人类迁徙过程, HPA可作为遗传标记应用于人类进化的研究。     

儿童免疫性血小板减少症血清中抗核仁抗体纯化以及靶抗原的筛选

免疫性血小板减少症为儿童常见获得性免疫性疾病,本研究前期发现有较高比例的抗核仁抗体阳性的儿童为免疫性血小板减少症患者。为筛选鉴定抗核仁抗体阳性免疫性血小板减少症患儿血清中抗核仁抗体识别的靶抗原,本研究利用HEP-2细胞系建立了细胞固定-抗体结合-抗体洗脱-抗体中和体系,成功纯化免疫性血小板减少症患儿血清中抗核仁抗体。利用蛋白免疫共沉淀和质谱分析法筛选出Ncl、Krt1、Krt2、Krt10等蛋白可能为免疫性血小板减少症患儿血清中抗核仁抗体结合的靶抗原。这些结果为免疫性血小板减少症患儿血清中抗核仁抗体靶抗原的鉴定提供有效方法,可进一步深化我们对免疫性血小板减少症发病机制的认识。     

狂犬病毒糖蛋白的克隆表达及其在中和抗体检测中的应用

目的:制备基因工程表达的狂犬病毒糖蛋白优势表位抗原,并评价其在疫苗免疫后中和抗体检测中的应用价值。方法:TRIzol法从狂犬病疫苗中提取总RNA,经RT-PCR获得糖蛋白目的基因片段,构建相应的原核表达质粒,转化大肠杆菌HB101,诱导表达获得纯化重组蛋白,以重组蛋白作为包被抗原,初步建立检测糖蛋白中和抗体的ELISA方法。结果:获得狂犬病毒糖蛋白优势表位区段抗原,建立了糖蛋白中和抗体ELISA检测方法。该检测方法对59例健康献血员血浆样本检测特异性为98.31%(58/59),接种狂犬疫苗免疫个体血浆样本抗体阳性率为98.95%(94/95)。结论:基因工程表达的狂犬病毒糖蛋白优势表位抗原可用于人接种狂犬疫苗后疫苗免疫效果评价。     

Polymorphisms in Canine Platelet Glycoproteins Identify Potential Platelet Antigens

Human alloimmune thrombocytopenic conditions caused by exposure to a platelet-specific alloantigen include neonatal alloimmune thrombocytopenia, posttransfusion purpura, and platelet transfusion refractoriness. More than 30 platelet-specific alloantigens have been defined in the human platelet antigen (HPA) system; however, there is no previous information on canine platelet-specific alloantigens. Using the HPA system as a model, we evaluated the canine ITGB3, ITGA2B, and GP1BB genes encoding GPIIIa (β₃), GPIIb (α_IIb), and GPIbβ, respectively, which account for 21 of 27 HPA, to determine whether amino acid polymorphisms are present in the orthologous canine genes. A secondary objective was to perform a pilot study to assess possible association between specific alleles of these proteins and a diagnosis of idiopathic thrombocytopenic purpura (ITP) in dogs. By using genomic DNA from dogs of various breeds with and without ITP, sequencing of PCR products encompassing all coding regions and exon–intron boundaries for these 3 genes revealed 4 single-nucleotide polymorphisms in ITGA2B resulting in amino acid polymorphisms in the canine genome, 3 previously reported and 1 newly identified (Gly[GGG]/Arg[AGG] at amino acid position 576 of ITGA2B. Of 16 possible ITGA2B protein alleles resulting from unique combinations of the 4 polymorphic amino acids, 5 different protein isoforms were present in homozygous dogs and explain all of the genotype combinations in heterozygous dogs. There was no amino acid polymorphism or protein isoform that was specific for a particular breed or for the diagnosis of ITP.Abbreviations: HPA, human platelet antigen; ITP, idiopathic thrombocytopenic purpura; PTR, platelet transfusion refractoriness; SNP, single-nucleotide polymorphismHuman alloimmune thrombocytopenic conditions caused by exposure to a platelet-specific alloantigen, through pregnancy or transfusion, include neonatal alloimmune thrombocytopenia, posttransfusion purpura, and platelet transfusion refractoriness (PTR). More than 30 platelet-specific alloantigens have been defined in the human platelet antigen (HPA) system, with 12 alloantigens grouped into 6 biallelic systems (HPA1 through HPA5 and HPA15) in which alloantibodies against both the common (designated ‘a’) and rare (designated ‘b’) alleles have been identified.^5,12 For the remaining 21 platelet alloantigens (HPA6bw through HPA14bw and HPA16bw through HPA27bw), only antibodies against the rare allele (designated ‘bw’) have been detected. Although HPA traditionally were defined by using immune sera, the molecular basis of these antigens has now been characterized.^5,12 The HPA reside in platelet membrane glycoproteins, the most common being GPIIIa, which accounts for 14 HPA. In all but one (HPA14bw), the platelet alloantigens are defined by a single amino-acid substitution caused by a single-nucleotide polymorphism (SNP) in the gene encoding the relevant membrane glycoprotein.^5,12 The Platelet Nomenclature Committee, which includes members of both the International Society of Blood Transfusion and the International Society of Thrombosis and Haemostasis, has set guidelines for defining new platelet antigens, which include: 1) determining the genetic basis of the alloantigen by genomic DNA sequence analysis, and 2) demonstrating an association between the genetic mutation and the reactivity of alloantibodies with the allelic forms of the protein.¹² For patients suspected of having alloimmune thrombocytopenia, well-defined platelet genotyping methods and serologic assays for the detection of platelet antibodies are available to guide case management.In contrast to the well-characterized HPA system and wealth of information on alloimmune thrombocytopenic conditions in humans, there is no information on canine platelet-specific alloantigens in the literature. However, early serologic studies using antiHPA1a alloantiserum resulted in direct immunoprecipitation of a 90-kDa protein from canine platelets, suggesting that the antigenic determinant for HPA1a has been conserved between humans and dogs.¹⁰ Neonatal alloimmune thrombocytopenia has not yet been documented in dogs, and there is a single case report of suspected posttransfusion purpura in a dog with hemophilia A, in which severe thrombocytopenia was noted 1 to 2 wk after transfusion (cryoprecipitate, fresh whole blood), with an increased amount of platelet surface-associated IgG and rapid resolution (less than 1 wk) of the thrombocytopenia.³⁰ PTR, however, has been well documented in dogs for more than 25 y, because this species has been used as an experimental model to evaluate a variety of methods of preventing platelet alloimmunization.^21-23 The occurrence of platelet alloimmunization in dogs receiving platelets from dog leukocyte antigen-identical littermates indicates that nondog leukocyte antigen immunizing platelet antigens, perhaps platelet-specific antigens, are responsible for the development of PTR.²¹Using the HPA system as a model, our main objective in this study was to evaluate the canine ITGB3, ITGA2B, and GP1BB genes encoding the GPIIIa (β₃), GPIIb (α_IIb), and GPIbβ, respectively, proteins that account for 21 of 27 HPA, to determine whether there are amino acid polymorphisms that could define canine platelet-specific alloantigens. A secondary objective was to perform a pilot study to assess the possible association between canine platelet antigen protein alleles or single amino acid substitutions and primary immune-mediated thrombocytopenia, also referred to as idiopathic thrombocytopenic purpura (ITP), in dogs. The identification of a canine platelet antigen system would improve our understanding of the molecular basis of alloimmune thrombocytopenic conditions in dogs and help guide effective platelet transfusion support of these critical patients.     

Modeling and Molecular Dynamics of HPA-1a and -1b Polymorphisms: Effects on the Structure of the β3 Subunit of the αIIbβ3 Integrin

Background

The HPA-1 alloimmune system carried by the platelet integrin αIIbβ3 is the primary cause of alloimmune thrombocytopenia in Caucasians and the HPA-1b allele might be a risk factor for thrombosis. HPA-1a and -1b alleles are defined by a leucine and a proline, respectively, at position 33 in the β3 subunit. Although the structure of αIIbβ3 is available, little is known about structural effects of the L33P substitution and its consequences on immune response and integrin functions.

Methodology/Principal Findings

A complete 3D model of the L33-β3 extracellular domain was built and a P33 model was obtained by in silico mutagenesis. We then performed molecular dynamics simulations. Analyses focused on the PSI, I-EGF-1, and I-EGF-2 domains and confirmed higher exposure of residue 33 in the L33 β3 form. These analyses also showed major structural flexibility of all three domains in both forms, but increased flexibility in the P33 β3 form. The L33P substitution does not alter the local structure (residues 33 to 35) of the PSI domain, but modifies the structural equilibrium of the three domains.

Conclusions

These results provide a better understanding of HPA-1 epitopes complexity and alloimmunization prevalence of HPA-1a. P33 gain of structure flexibility in the β3 knee may explain the increased adhesion capacity of HPA-1b platelets and the associated thrombotic risk. Our study provides important new insights into the relationship between HPA-1 variants and β3 structure that suggest possible effects on the alloimmune response and platelet function.     

Sensitive detection of idiotypic platelet-reactive alloantibodies by an electrical protein chip

To prevent and treat immune-mediated platelet disorders (e.g. neonatal allo-immune thrombocytopenia and platelet transfusion refractoriness) the causative idiotypic platelet-reactive antibodies have to be detected with high sensitivity and specificity. The "Monoclonal Antibody Immobilization Platelet Assay" (MAIPA) is the diagnostic gold standard for immunotyping sera with respect to alloantibodies against human platelet antigens (HPA). However, it is labor-intensive and time-consuming. In this work, an automated protein chip assay (enzyme-linked sandwich immunoassay) based on interdigitated gold microelectrodes in combination with an electrical read-out system was developed and optimized. For this purpose, specific capture antibodies were immobilized on the gold electrodes. The binding of the target is detected via an enzyme-labeled detection antibody by a redox-recycling process that corresponds to the amount of bound target molecule. With this electrical chip assay it is possible to detect antibodies against HPA-1a, HPA-5b and HLA with high sensitivity and specificity in less than half the duration of the MAIPA protocol with similar intra- and interassay variance.     

Optimized sensitivity of allele-specific PCR for prenatal typing of human platelet alloantigen single nucleotide polymorphisms

PCR using sequence-specific primers (PCR-SSP) is widely employed for the genotyping of single nucleotide polymorphisms (SNPs) in both routine diagnosis and medical research. The human platelet alloantigens (HPAs) represent SNPs in platelet-specific glycoproteins, and HPA-1, -2, -3, and -5 are the most relevant in immunohematology. In most protocols, the respective HPA-SNPs are analyzed in allele-specific reactions, each with at least 100 ng DNA. In many cases, prenatal HPA typing in the diagnosis of neonatal alloimmune thrombocytopenia is often limited by the restricted amounts of fetal DNA that are obtainable. We developed a novel PCR-SSP technique to achieve accurate HPA genotypes using only 1 ng DNA per reaction. The concentration of HPA-specific primers was increased to 1 microM each and exhibited a higher sensitivity compared to a commercial PCR-SSP kit. The modified PCR-SSP technique enabled the identification of fetal HPA genotypes using only 0.5 mL amniotic fluid (from week 16 of gestation) and from a maternal plasma sample (from week 38 of gestation). The principle of the modified PCR-SSP technique may also be applied for the genotyping of other SNPs from limited amounts of DNA.     

Molecular basis for nonphenylketonuria hyperphenylalaninemia.

Nonphenylketonuria hyperphenylalaninemia (non-PKU HPA) is defined as phenylalanine hydroxylase (PAH) deficiency with blood phenylalanine levels below 600 mumol/liter (i.e., within the therapeutic range) on a normal dietary intake. Haplotype analysis at the PAH locus was performed in 17 Danish families with non-PKU HPA, revealing compound heterozygosity in all individuals. By allele-specific oligonucleotide (ASO) probing for common PKU mutations we found 12 of 17 non-PKU HPA children with a PKU allele on one chromosome. To identify molecular lesions in the second allele, individual exons were amplified by polymerase chain reaction and screened for mutations by single-strand conformation polymorphism. Two new missense mutations were identified. Three children had inherited a G-to-A transition at codon 415 in exon 12 of the PAH gene, resulting in the substitution of asparagine for aspartate, whereas one child possessed an A-to-G transition at codon 306 in exon 9, causing the replacement of an isoleucine by a valine in the enzyme. It is further demonstrated that the identified mutations have less impact on the heterozygote's ability to hydroxylate phenylalanine to tyrosine compared to the parents carrying a PKU mutation. The combined effect on PAH activity explains the non-PKU HPA phenotype of the child. The present observations that PKU mutations in combination with other mutations result in the non-PKU HPA phenotype and that particular mutation-restriction fragment length polymorphism haplotype combinations are associated with this phenotype offer the possibility of distinguishing PKU patients from non-PKU individuals by means of molecular analysis of the hyperphenylalaninemic neonate and, consequently, of determining whether a newborn child requires dietary treatment.     

Serotonin transporter gene variation, infant abuse, and responsiveness to stress in rhesus macaque mothers and infants

A functional polymorphism in the promoter region of the serotonin transporter (5-HTTLPR) gene has been associated with variation in anxiety and hypothalamus-pituitary-adrenal (HPA) axis function in humans and rhesus macaques. Individuals carrying the short allele are at a higher risk for developmental psychopathology, and this risk is magnified in short allele carriers who have experienced early life stress. This study investigated the relationship between 5-HTTLPR allelic variation, infant abuse, and behavioral and hormonal responses to stress in rhesus macaques. Subjects were 10 abusive mothers and their infants, and 10 nonabusive mother-infant pairs. Mothers and infants were genotyped for the rh5-HTTLPR, and studied in the first 6 months of infant life. For mothers and infants, we measured social group behavior, behavioral responses to handling procedures, and plasma concentrations of ACTH and cortisol under basal conditions and in response to stress tests. The proportion of individuals carrying the short rh5-HTTLPR allele was significantly higher among abusive mothers than controls. Among mothers and infants, the short allele was associated with higher basal cortisol levels and greater hormonal stress responses in the infants. In addition, infants who carried the short rh5-HTTLPR allele had higher anxiety scores than infants homozygous for the long allele. The rh5-HTTLPR genotype also interacted with early adverse experience to impact HPA axis function in the infants. These results are consistent with those of previous studies which demonstrate associations between serotonergic activity and anxiety and stress reactivity, and add additional evidence suggesting that genetic variation in serotonergic function may contribute to the occurrence of abusive parenting in rhesus macaques and modulate emotional behavior and HPA axis function.     

猪钙蛋白酶抑制蛋白基因的基因型与肉质性状的关联性分析

钙蛋白酶抑制蛋白基因是影响猪肉质性状的候选基因之一。本研究以125头地方猪和117头外来猪为材料,研究CAST基因的多态性。结果在CAST基因上检测到一个多态性位点(A876G),并引起了氨基酸残基的改变Lys250 Arg。在地方猪种中仅检测到G (Arg)等位基因,而在外来猪种中A (Lys) 和 G (Arg)两个等位基因均检测到。基因型与肉质性状的关联性分析结果表明,CAST基因型与肌肉的嫩度,屠宰45 min后的pH值及滴水损失存在强相关,又由于地方猪种与外来猪种的肉质性状间存在显著差异。因此,在CAST基因上检测到的多态型位点Lys250Arg的基因型效应有待于进一步研究,并将其有效应用于商品猪生产中。     

Differential gene silencing by trans-heterochromatin in Drosophila melanogaster.

The brown(Dominant) (bw(D)) allele contains a large insertion of heterochromatin leading to the trans-inactivation of the wild-type allele in bw(D)/bw(+) heterozygous flies. This silencing is correlated with the localization of bw(+) to a region of the interphase nucleus containing centric heterochromatin. We have used a series of transgene constructs inserted in the vicinity of the bw locus to demarcate both the extent of bw(D) influence along the chromosome and the relative sensitivities of various genes. Examples of regulatory regions that are highly sensitive, moderately sensitive, and insensitive were found. Additionally, by using the same transgene at increasing distances from the bw(D) insertion site in trans we were able to determine the range of influence of the heterochromatic neighborhood in terms of chromosomal distance. When the transgene was farther away from bw, there was, indeed, a tendency for it to be less trans-inactivated. However, insertion site also influenced silencing: a gene 86 kb away was trans-inactivated, while the same transgene 45 kb away was not. Thus location, distance, and gene-specific differences all influence susceptibility to trans-silencing near a heterochromatic neighborhood. These results have important implications for the ability of nuclear positioning to influence the expression of large blocks of a chromosome.