甘露聚糖结合凝集素基因多态性与血清蛋白表达水平的关系

目的了解汉族儿童甘露聚糖结合凝集素(MBL)第一外显子54密码子的基因多态性以及与血清MBL蛋白水平的关系。方法用ELISA方法检测71例儿童血清MBL水平,用聚合酶链反应-限制性内切酶片段长度多态性分析(PCR-RFLP)方法对第一外显子54密码子基因多态性进行分析,比较不同基因型的血清蛋白质表达水平,并测定部分PCR产物的核苷酸序列。结果汉族人群MBL基因第1外显子54密码子3种基因型为GGC/GGC(77.5%)、GGC/GAC(18.3%)、GAC/GAC(4.2%),等位基因GGC(0.87)出现频率较GAC(0.13)高;低MBL水平基因型为GGC/GGC(12.5%)、GGC/GAC(75.0%)、GAC/GAC(12.5%),GGC/GAC基因型及等位基因GAC(0.50)频率较正常MBL组(0.03)高(P<0.005);GGC/GGC基因型的血清MBL的水平比GGC/GAC基因型明显增高[(3.67±2.10)μg/ml,(0.10±0.05)μg/ml,P<0.001],GGC/GGC基因型汉族人群血清水平较巴布亚新几内亚人[Papua NewGuinea,(2.45±0.82)μg/ml]明显增高(P<0.001);发现MBL第一外显子15、21、58、61密码子的突变。结论第一外显子第54密码子表现不同基因多态性分布,并对应不同的血清MBL水平。主要是GGC/GAC导致低血清MBL水平,但可能存在除52、54、57密码子外的第一外显子其他部位的基因多态性导致血清MBL蛋白质表达的种族差异。     

慢性HBV感染者甘露糖结合蛋白基因多态性与疾病进展及与HBV DNA相关性的研究

目的 探讨慢性HBV感染者甘露糖结合蛋白(MBP)基因多态性对慢性乙型肝炎患者疾病进展的影响及与HBV DNA载量的关系.方法 采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)方法和实时荧光定量PCR(FQ-PCR)技术对244例慢性乙型肝炎患者、151例肝硬化患者和88名正常对照者的MBP基因第54号密码子多态性和血清HBV DNA载量进行检测.结果 CHB轻、中度组患者MBP基因GGC/GAC基因型频率和GAC等位基因频率与正常对照组比较差异无统计学意义(P＞0.05);CHB重度组、代偿性LC组、失代偿性LC组MBP基因GGC/GAC基因型频率和GAC等位基因频率显著高于正常对照组(P＜0.05);其中失代偿性LC组突变率最高,为36.5％.慢性HBV感染者MBP基因GGC/GAC基因型频率和GAC等位基因频率不随HBV DNA载量而变化(P＞0.05).结论 MBP基因第54号密码子突变与HBV DNA载量无明显关系,而与慢性HBV感染进展有关.     

甘露糖结合蛋白基因多态性在IgA肾病肾组织免疫沉积多样性形成中的作用

目的 探讨甘露糖结合蛋白（mannose-binding protein,MBP)基因第54号密码子GGC→GAC变异在IgA肾病（IgA nephropathy,IgAN)患者肾小球免疫沉积多样性形成中的作用。方法 选取140名正常健康成人,147例IgAN患者,其中77例为单纯IgA伴C3沉积（A组）,70例为IgA,IgG,IgM伴C3、C1q沉积（AGM组）。使用PCR－RFLP法分析MBP基因型;同时应用ELISA法对58例IgAN患者和32名正常人血清MBP浓度进行了测定,分析比较MBP不同基因型与其血清浓度之间的关系。结果 （1）MBP基因GAC型等位基因与IgAN的大量免疫沉积明显相关（OR＝1.95,95%CI:1.06-3.58).（2）无论在A组还是在AGM组,GAC等位基因携带者中起病时有前驱感染史者均显著多于GGC合子（P＜0．05）。（3）不同人群中,GGC／GGC型血清MBP水平均明显高于GGC／GAC型（P＜0．0001）,GAC／GAC型血清MBP水平接近于0。结论 IgAN患者肾小球免疫沉积物的类型与MBP基因多态性密切相关。不同个体先天性防御屏障功能的差异在IgAN肾小球免疫沉积多样性的形成中发挥了重要作用。     

广东地区汉族人MBL基因GGC54GAC点突变的初步筛查

目的对广东地区汉族人群的甘露聚糖结合凝集素结构基因第一外显子第54位密码点突变(GGC54GAC)进行初步筛查.方法提取外周血白细胞DNA进行相应片段的PCR扩增,再对产物进行单链构象多态性分析.结果在166人中查出野生型纯合子147例,占88.55%,GGC54GAC突变杂合子19例,占11.45%,未发现GGC54GAC突变纯合子.结论广东地区汉族人群MBL基因GGC54GAC突变频率为0.057.     

中国五个民族的甘露糖结合蛋白基因多态性特点及意义

目的 分析中国5个民族人群中甘露糖结合mannose-binding protein,MBP)基因多态性特点,并比较汉族慢性乙型肝炎患者与健康对照之间MBP基因多态性的差异,方法 应用聚合酶锭瓜在-限制性内切酶片段长度多态性分析,对中国5个民族的955份样品的MBP基因多态性进行检测,并将22份汉族人样品的PCR产物直接进行DNA序列分析。结果 报告了中国汉族人MBP基因第1外显子及其两侧附近的DNA序列;5个民放MBP基因密码子54（MBP-54）等位基因突变频率分别为：汉族0.181、维吾尔族0.128、蒙古族0.181、藏族0.179和彝族0.181;5个民族的MBP-54基因多态性分布均符合Hardy-Weinberg平衡;与汉族人群相比,维吾尔族的MBP-54等位基因多态性和等位基因频率的差异无显著性。所有人群中未检测到密码子52和57基因突变。结论 在所调查的5个民族中,存在较高比例的MBP-54基因突变。MBP基因的缺失并不与慢性乙型肝炎相关联。     

湖北汉族人群甘露糖结合凝集素基因外显子1多态性与SLE关联性的研究

目的：分析湖北汉族人群甘露糖结合凝集素(Mannose-Binding LectionL或Mannose-Binding Protein,MBL或MBP)基因外显子1多态性，探讨其与系统性红斑狼疮(Systemic Lupus Erythematosus,SLE)的易感性关系。方法：采用异源双链杂交技术对111例健康正常人和41例SLE患者的MBL基因外显子1多态性进行分析。结果：①共检测出两种等位基因：野生型A和变异型B(在54位密码子由GGC→GAC)，未检出变异型C、D等位基因。②正常对照中A等位基因及B等位基因的基因频率分别为0．910和0．090，符合Hardy-Wernberg定律；与此前在日本人中报道的A及B等位基因频率0．767和0．233相比，变异型B的等位基因频率明显低于后者(P＜0．05)。③SLE病人组中B等位基因频率为0．146，高于正常对照组，但差异无显著性意义。结论：在湖北汉族人群中MBL基因外显子1具有遗传多态性，而且与已知其他人群的分布频率有一定差异。MBL基因外显子1的遗传多态性并不与系统性红斑狼疮相关联。     

广东地区汉族人MBL基因点突变的研究

目的：研究我国汉族人群甘露聚糖结合凝集素（MBL）结构基因外显子1第52、54、57位密码点突变（CGT52TGT、GGC54GAC和GGA57GAA）。方法：收集广东地区汉族普通人群的血标本，提取白细胞基因组DNA，以PCR扩增目的基冈片段，应用荧光探针杂交可视技术检测其MBL基因的点突变。结果：从202份样本中，检出GGC54GAC点突变纯合子6例和杂合子44例（等位基因频率为0．139），GGA57GAA点突变杂合子1例（频率为0．002），未发现CGT52TGT点突变（频率为0）。结论：广东地区汉族人群MBL基因点突变的频率较高，为防治MBL缺损病提供了一定的实验依据。     

山西汉族正常人群ACE基因多态性频率的分布

目的应用RFLP方法研究ACE基因插入/缺失（I/D）多态性在山西地区360例汉族正常人群中的频率分布。结果显示等位基因频率Ⅰ：62.4%、D：37.6%,各基因型频率分别为：Ⅱ38.1%、ID46.6%、DD13.3%,各基因型频率与新加坡人、日本人、台湾地区、香港的华人接近,与英国白人和非洲籍人群差异显著。表明ACE基因多态性的分布有明显的种族和地区差异。     

GSTT1基因多态性与IgA肾病易感性的研究

目的：了解谷胱甘肽硫转移酶T1（glutathion S-transferase-theta）基因多态性与内蒙古包头地区汉族人群IgA肾病易感性的相关性。方法：利用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）技术检测。随机收集包头医学院第一附属医院肾内科IgA肾病患者110例为病例组,健康体检正常者113例作为对照组。结果：GSTT1基因缺失型频率在IgA肾病患者组中为49.1%（54/110）;在正常人体检组中为53.1%（60/113）,（χ2=1.527,P〉0.05）。二者之间差异无统计学意义。结论：GSTT1基因多态性与内蒙古包头地区汉族人群IgA肾病发生无相关性。     

中国汉族、维吾尔族人群甘露聚糖结合凝素基因多态性的检测

分别收集广东省汉族和新疆维吾尔族自治区维吾尔族一般人群血标本,提取白细胞基因组DNA,以多聚酶链反应扩增目的基因片段,应用荧光探针杂交可视技术检测其甘露聚糖结合凝集素(MBL)基因54位密码点突变(GGC54GAC)。从138份汉族样本中检出GGC54GAC突变型纯合子4例,占2.9%,杂合子30例,占21.74%;120份维吾尔族标本中,检出突变型纯合子3例,占2.5%,杂合子34例,占28.33%。因此,汉族和维吾尔族人群MBL基因GGC54GAC突变的频率分别为0.138和0.167,两民族间无明显差异。     

Gene frequency and partial protein characterization of an allelic variant of mannan binding protein associated with low serum concentrations.

Low plasma concentration of mannan binding protein (MBP) has been shown to be the basis for a common opsonic deficiency and suggested to be caused by a single nucleotide substitution at base 230 of exon 1 in the MBP gene. This substitution causes a replacement of glycine (codon GGC) with aspartic acid (codon GAC). Of 123 healthy Danish individuals investigated by polymerase chain reaction performed on exon 1, followed by restriction fragment length polymorphism or allospecific probing, 93 were homozygous (75.6%) for GGC, 28 heterozygous (22.8%), and two homozygous for GAC (1.6%). The gene frequency of the GAC allele was found to be 0.13. DNA sequencing of the cloned exon 1 from one GAC homozygous individual revealed no other substitution. The median MBP concentration in the group containing the GAC allele was 6.4 times lower than in the GGC homozygous group (195 and 1234 micrograms/l respectively). However, the range in plasma concentrations of MBP was wide and overlapping between the groups. MBP protein was detected in both the GAC homozygotes (9 and 387 micrograms/l). Furthermore, no difference in relative mass and biological activity (mannan binding) was found when sera containing the two forms of MBP were investigated. Accordingly, it can be concluded that the GAC allele is able to produce a functional MBP protein which may be detected in serum at low concentrations.     

Diallelic polymorphism may explain variations of the blood concentration of mannan-binding protein in Eskimos, but not in black Africans.

Mannan-binding protein (MBP) is a lectin which, upon binding to certain carbohydrates, activates the classical pathway of complement without the involvement of antibody or C1q. Deficiency of the MBP is associated with an opsonic defect and recurrent infections during early life. An amino acid substitution in the exon 1 at codon 54 in the MBP gene (GGC [glycine] to GAC [aspartic acid]) has been shown to be closely associated with low MBP concentration in Caucasoids. The gene frequency of the mutant allele in this population has been estimated at 0.13. In the study described here, we investigated the association between the mutant allele and MBP protein concentration in Eskimos from East-Greenland and black Africans from the Baringo District in Kenya. The frequency of the GAC allele was identical in Eskimos and Caucasoids (0.13). No overlap with regard to MBP concentration between the genotypes was found in the Eskimos. In contrast, the Africans revealed a low frequency of the GAC allele (0.009). However, the median MBP protein concentration was approximately 5 times lower among the Africans than the Eskimos. In 12.6% of the Africans and in 2.5% of the Eskimos, MBP was undetectable. Thus, MBP deficiency is the most frequent immunodeficiency so far described. The high prevalence of MBP deficiency among healthy individuals indicates that MBP deficiency also confers some selective advantages. We advance the hypothesis that MBP deficiency is maintained in populations because MBP deficiency decreases the infectivity of some intracellular micro-organisms which are dependent on opsonization.     

DIALLELIC POLYMORPHISM MAY EXPLAIN VARIATIONS OF THE BLOOD CONCENTRATION OF MANNAN-BINDING PROTEIN IN ESKIMOS,BUT NOT IN BLACK AFRICANS

Mannan-binding protein (MBP) is a lectin which, upon binding to certain carbohydrates, activates the classical pathway of complement without the involvement of antibody or C1q. Deficiency of the MBP is associated with an opsonic defect and recurrent infections during early life. An amino acid substitution in the exon 1 at codon 54 in the MBP gene (GGC [glycine] to GAC [aspartic acid]) has been shown to be closely associated with low MBP concentration in Caucasoids. The gene frequency of the mutant allele in this population has been estimated at 0.13. In the study described here, we investigated the association between the mutant allele and MBP protein concentration in Eskimos from East-Greenland and black Africans from the Baringo District in Kenya. The frequency of the GAC allele was identical in Eskimos and Caucasoids (0.13). No overlap with regard to MBP concentration between the genotypes was found in the Eskimos. In contrast, the Africans revealed a low frequency of the GAC allele (0.009). However, the median MBP protein concentration was approximately 5 times lower among the Africans than the Eskimos. In 12.6% of the Africans and in 2.5% of the Eskimos, MBP was undetectable. Thus, MBP deficiency is the most frequent immunodeficiency so far described. The high prevalence of MBP deficiency among healthy individuals indicates that MBP deficiency also confers some selective advantages. We advance the hypothesis that MBP deficiency is maintained in populations because MBP deficiency decreases the infectivity of some intracellular micro-organisms which are dependent on opsonization.     

Association between mannose-binding lectin deficiency and septic shock following acute pyelonephritis due to Escherichia coli

Structural and promoter MBL2 gene polymorphisms responsible for low MBL levels are associated with increased risk of infection. The objective of this study was to assess the possible association between polymorphisms of the MBL2 gene and the incidence of septic shock and bacteremia in patients with acute pyelonephritis due to Escherichia coli. The study included 62 female patients with acute pyelonephritis due to E. coli who required hospital admission, as well as 133 healthy control subjects. Six single-nucleotide polymorphisms (-550 G/C, -221 C/G, +4 C/T, codon 52 CGT/TGT, codon 54 GGC/GAC, and codon 57 GGA/GAA) in the MBL2 gene were genotyped by using a sequence-based typing technique. No significant differences were observed in the frequencies for low-expression MBL2 genotypes (O/O and LXA/O) between patients with acute pyelonephritis and healthy controls. Patients with acute pyelonephritis and septic shock had a higher incidence of low-expression MBL2 genotypes than patients with acute pyelonephritis without septic shock (odds ratio = 9.019, 95% confidence interval = 1.23 to 65.93; P = 0.03). No association was found between bacteremic acute pyelonephritis and low-expression MBL2 genotypes. We found that low-expression MBL2 genotypes predispose to septic shock but not to bacteremia in patients with E. coli-induced acute pyelonephritis. Determination of MBL2 polymorphisms could be useful for assessing the risk of septic shock in women undergoing acute pyelonephritis.     

中国维吾尔族人群MBL基因启动子及第一外显子区SNP及其单倍型与基因型研究

收集新疆维吾尔族自治区维吾尔族一般人群血标本,提取白细胞基因组DNA,以序列特异性引物-多聚酶链反应技术检测其甘露聚糖结合凝集素(MBL)基因启动子区单核苷酸多态性位点-550G/C(称H/L等位基因)、-221C/G(X/Y)、+4C/T(P/Q)和结构基因第一外显子点突变CGT52TGT、GGC54GAC和GGA57GAA(分别称为D、B、C等位基因,野生型即A等位基因),并分析其单倍型与基因型。发现MBL基因启动子区等位基因主要为L、Y、P,第一外显子等位基因只发现B,未检出C和D;检出5种单倍型,其频率分别是HYPA 0.282、LYPA 0.268、LXPA 0.260、LYPB 0.120、LYQA 0.070。检出12种基因型,其频率分别为HYPA/HYPA 0.183、LXPA/LXPA 0.141、LYPA/LYQA 0.113、LYPA/LYPA 0.112、LYPA/LXPA 0.085、HYPA/LYPA 0.085、LXPA/LYPB 0.085、HYPA/LXPA 0.070、HYPA/LYPB 0.042、LYPA/LYPB 0.028、LYPB/LYQA 0.028、YPB/LYPB 0.028。