蒙古族人MBL基因exon I 54位密码子点突变频率与其血浆含量的相关性

目的 :初步调查健康蒙古族人甘露 (聚 )糖结合凝集素 (MBL)基因 5 4位密码子点突变的情况 ,检测其血浆MBL的含量 ,探讨两者的相关性。方法 :根据MBL基因序列设计引物 ,建立MBL基因点突变的检测方法 (即PCR RFLP)。用MBLOligomerELISA试剂盒测定血浆MBL的浓度。结果 :建立了特异、敏感的检测MBL基因 5 4位密码子点突变的方法 ,测得健康蒙古族人该基因的突变频率为 0 .18;血浆MBL含量的平均值为(2 .5 3± 1.96 )mg/L ,两者呈负相关 (r=- 0 .6 4 1)。结论 :所建立的测定MBL基因 5 4位密码子点突变的PCR RFLP方法 ,特异性高、重复性好、较灵敏 (最低检出量为 16 0pgDNA) ,并证明该基因的突变频率与其血浆MBL的含量呈负相关。     

北方回族人MBL 54位密码子基因多态性及血浆含量相关性

目的：初步调查北方地区健康回族人群MBL基因ExonI54位密码子点突变的情况，检测其血浆MBL含量，探讨二者的相关性。方法：用PCR—RFLP方法检测MBL基因点突变频率；用MBL OligomerELISA试剂盒测定出血浆MBL的浓度。结果：测得健康回族人该基因突变频率为0．15；血浆MBL含量的平均值为3．40mg／L；二者呈负相关（r=-0．67）。结论：健康回族人MBL基因54位密码子点突变频率与其血浆含量呈负相关。     

GGC54GAC MBL突变体的构建

目的：在人甘露聚糖结合凝集素（MBL）基因中引入GGC54GAC点突变。方法：设计上下游引物和诱变引物,以汉族人野生型MBLcDNA为模板,采用megaprimer-PCR技术进行定点突变。将PCR产物克隆至pGEM-T载体,酶切和测序分析。结果：以上游引物和诱变引物进行第一轮PCR,获得一约180bp的DNA片段,以此片段和下游引物行第二轮PCR扩增,得到一长约780bp的产物,将其克隆至pGEM-T载体,酶切了现第54位密码中的BanI酶切位点已被破坏,与计算机酶切图谱分析结果一致。序列分析表明,除第54位密码变为GAC外,余与野生型MBL cDNA完全相同。结论：构建成功了GGC54GAC MBL突变体,为深入探索MBL基因突变引起调理吞噬缺损的机制提供了分子病理模型。     

血管紧张素原基因235位密码子多态性与原发性高血压关系的研究

采用人工修饰过碱基序列的引物及错配PCR方法 ,加上内切酶酶切和电泳 ,分析了高血压患者组和家系同胞健康对照组的血管紧张素原 (AGT)基因 2 35位密码子的基因型分布及等位基因频率 ,经比较研究。结果　提示AGT基因2 35位密码子的TT型和T等位基因频率在高血压患者组略升高 ,但未见统计学意义上的差异 (P >0 .0 5 ) ;而在中重度高血压组中 ,AGT基因 2 35位密码子的TT型和T等位基因频率 ,均比轻度高血压组有显著升高 (P <0 .0 5和P <0 .0 1)。结论　在中、重度高血压的发病中 ,AGT2 3 5基因型多态性可能起着重要的作用。     

精神分裂症患者MBL基因ExonI 54位密码子点突变频率与血清水平的研究

目的探讨精神分裂症患者血清MBL水平与基因突变的相关性,了解MBL在患者免疫病理机制中的作用。方法应用ELISA法检测血清MBL水平;利用PCR产物直接测序的方法检测MBL基因外显子Ⅰ第54位密码子(MBL-54)的点突变频率。结果精神分裂症患者血清MBL水平(1367.218±1277.429ng/mL)明显低于对照组(1987.781±976.748ng/mL)(t=2.888,P=0.047)。MBL-54基因型GGC/GGC突变频率(55.77%)低于对照组(69.23%)(χ^2=2.010,P=0.224);GGC/GAC型突变频率(42.31%)高于对照组的(28.85%)(χ^2=2.298,P=0.315);GGC/GAC型的患者血清MBL水平(1034.52±529.72ng/mL)明显低于对照组(2195.81±1275.38ng/mL)(t=3.336,P=0.0039)。结论精神分裂症患者血清低水平的MBL可能与MBL-54基因型GGC/GGC突变率减低,GGC/GAC突变率升高的综合作用相关,MBL可能是患者体内CIC滞留或清除障碍的分子机制之一。     

50株淋病奈瑟菌喹诺酮耐药决定区的DNA测序研究

目的　从基因水平了解淋病奈瑟菌 (NeisseviaGonorrhoeae ,NG )对喹诺酮类药物的耐药状况。方法　对收集自常州地区的 5 0株NG喹诺酮作用靶位酶 (DNA回旋酶 )GyrA基因进行PCR检测 ;并对喹诺酮耐药决定区 (quinoloneresis tance—determingregion ,QRDR )进行测序研究。结果　 5 0株NG菌经GyrA基因扩增均出现 372bp清晰明亮的荧光带 ,其产物经双脱氧末端终止法测序经与 (gi:5 2 940 7)序列比对 ,5 0株NG菌均存在第 91位和第 95位密码子的突变 ,第 91位密码子均由TTC→TCC ;第 95位密码子由GAC→GGC、GCC和AAC三种形式。结论　本文基因研究显示喹诺酮类抗生素对我国淋病的治疗已失去作用 ,在喹诺酮类新型药物研制中要加强对突变株的作用     

46,XY女性性反转患者分子遗传学诊断

目的探讨46,XY女性性反转患者的发病机制.方法应用PCR扩增SRY基因;PCR产物通过限制性酶切-单链构象多态性方法检测未知突变;基因测序以进一步明确突变.结果11例46,XY女性患者中检出2例SRY基因缺失,9例46,XY女性患者PCR扩增出现609bp特异性片段,通过限制性酶切-单链构象多态性方法检测发现其中1例患者单链电泳带发生变异;基因克隆测序分析表明HMG盒内第244位核苷酸的位置存在点突变(A→T),导致第82位密码子发生错义突变,由原来编码天冬酰胺Asn(AAT)变为编码酪氨酸Tyr(TAT).结论SRY基因的研究有助于阐明46,XY女性性反转的发病机理,为临床确诊提供科学依据.     

p53基因第7外显子点突变与乳腺癌的关系

目的：研究ｐ５３基因点突变与乳腺癌发生发展关系。该当：应用多聚酶链反应－限制性片段长度多态性（ＰＣＲ－ＲＦＬＰ）检测７５例人乳腺癌标本ｐ５３基因第７外显子内２４８，２４９位密码子的点突变，结果：７５例乳腺癌标本ｐ５３基因第７外显子全长序列ＣＲ扩增产物经限制性内切酶ＭｓｐＩ酶切后，发现２例为突变型，用ＨａｅⅡ酶切后未发现有突变，结论：上述结果揭示ｐ５３基因第７外显子内２４８位密码子的突变为乳腺癌ｐ５     

汉族人甘露聚糖结合凝集素全长基因的克隆与序列分析

目的 克隆汉族人甘露聚糖结合凝集素(MBL)全长基因.方法 提取汉族人白细胞基因组DNA,高保真PCR扩增MBL基因,应用TA克隆方法将PCR产物与载体pcR(R)-XL-TOPO连接,经DNA测序后利用软件DNAStar进行分析.结果 MBL基因反向插入pCR(R)-XL-TOPO,全长6 321 bp,与GenBank收录的基因序列相比,有17个碱基不同,其中仅1个位于编码区(外显子4),但编码的氨基酸没有改变,且该碱基恰与GenSank收录的人MBL cDNA一致,此序列已被GenBank收录,登录号EU596574.结论成功克隆了汉族人MBL基因全长序列,其结构基因的基因型属于野生型,这为研究MBL基因非编码区对MBL表达的影响奠定了基础.     

3个肾上腺脑白质营养不良家系的基因突变分析

目的　对 3个肾上腺脑白质营养不良 ( adrenoleukodystrophy,AL D) ( MIM# 30 0 10 0 )家系进行基因突变分析。方法　从 3个 AL D患儿及其主要家系成员的外周血白细胞 ,提取总 RNA和基因组 DNA。应用逆转录聚合酶链反应技术 ,对 3个家系的 ABCD1基因编码区 ,分 4个片段进行 PCR扩增并对 PCR产物直接测序。同时应用 PCR-限制性酶切或扩增阻滞突变系统分析相应的基因组 DNA,进一步确证ABCD1基因的突变位点。结果　 3名患儿的 ABCD1基因上均存在错义突变 ,其中患儿 1的 ABCD1基因第 5 34位密码子发生 CCC→ CGC改变 ,使脯氨酸被精氨酸取代 ( P5 34R) ;患儿 2的 ABCD1基因第 2 6 6位密码子发生 GGG→AGG改变 ,使甘氨酸被精氨酸取代 ( G2 6 6 R) ;患儿 3母亲的 ABCD1上一个等位基因第 6 17位密码子发生 CGC→ GGC改变 ,使精氨酸被甘氨酸取代 ( R6 17G) ,另一个等位基因未发生突变。结论　在中国人 AL D患者中发现 1个新的 ABCD1基因突变 ( P5 34R) ,并首次在中国人 AL D患者中检测到G2 6 6 R、R6 17G突变     

Relationship between gene polymorphisms of mannose-binding lectin (MBL) and two molecular forms of MBL

Mannose-binding lectin (MBL) activates complement through MBL-associated serine proteases (MASP). A deficiency in MBL due to mutations at exon 1 of the human MBL gene is reported to cause vulnerability to infection. We examined sera of known MBL genotype by gel filtration and assessed their elution patterns using an ELISA for MBL and identified two MBL forms, a high-molecular-mass form and a lower-molecular-mass form. By the identification of either or both forms in individual sera, three types of patterns emerged: type 1 consisted of a high-molecular form; type 2, of a low-molecular form; and type 3, of both forms. Types 1, 2 and 3 corresponded, respectively, to a wild type (A/A), a homozygous mutation at codon 54 (B/B) and their heterozygote (A/B). One exception was a heterozygous LXPA/LYPB phenotype that exhibited the type-2 pattern. Binding to mannan and MASP-1/3 occurred exclusively with the high-molecular form. An apparent MBL deficiency does not in fact representa deficiency in MBL molecules but rather the presence of circulating oligomeric mutant MBL with impaired function.     

MASP interactions with plasma-derived MBL

The interaction of mannan-binding lectin (MBL) with its associated serine proteases (MASPs) was investigated using recombinant (r) MBL, plasma-derived (pd) MBL, rMASP-3 and rMAp19. When mixed with MBL-deficient serum, rMBL and pdMBL associated with free MASP-2 to (re)gain complement-activating activity. MASPs already associated with pdMBL did not exchange with rMASP-3 or rMAp19, which bound to non-overlapping sites on MBL. Thus, rMASP-3 and rMAp19 bound to free available sites on rMBL and pdMBL. These results have important implications for the therapeutic use of MBL preparations.     

MBL1 gene in nonhuman primates

With the aim of investigating the evolution of MBL1P1 (MBL1) gene, we analyzed the MBL1 coding region sequences in several specimens of two species of great apes, two species of Hylobatidae, four species of Cercopithecidae, and one Platyrrhine species, and in human beings. An indication for a progressive silencing of the molecule has been found. We found a ～300 bp insertion in the first intron of MBL1 in the Cercopithecidae that could explain the different splicing between primates species and possibly why Macaca mulatta is able to produce a complete protein, whereas in human beings the protein product is truncated. Based on our genetic findings, we could speculate that all the Cercopithecidae (presenting the 300-bp insertion) may express MBL1 mature protein like the M mulatta, whereas the lesser and great apes, which lack this insertion as do human beings, may have only the truncated pseudogene.     

Mannose binding lectin (MBL) and HIV

The envelope protein (gp120/gp41) of HIV-1 is highly glycosylated with about half of the molecular mass of gp120 consisting of N-linked carbohydrates. While glycosylation of HIV gp120/gp41 provides a formidable barrier for development of strong antibody responses to the virus, it also provides a potential site of attack by the innate immune system through the C-type lectin mannose binding lectin (MBL) (also called mannan binding lectin or mannan binding protein). A number of studies have clearly shown that MBL binds to HIV. Binding of MBL to HIV is dependent on the high-mannose glycans on gp120 while host cell glycans incorporated into virions do not contribute substantially to this interaction. It is notable that MBL, due to its specificity for the types of glycans that are abundant on gp120, has been shown to interact with all tested HIV strains. While direct neutralization of HIV produced in T cell lines by MBL has been reported, neutralization is relatively low for HIV primary isolates. However, drugs that alter processing of carbohydrates enhance neutralization of HIV primary isolates by MBL. Complement activation on gp120 and opsonization of HIV due to MBL binding have also been observed but these immune mechanisms have not been studied in detail. MBL has also been shown to block the interaction between HIV and DC-SIGN. Clinical studies show that levels of MBL, an acute-phase protein, increase during HIV disease. The effects of MBL on HIV disease progression and transmission are equivocal with some studies showing positive effects and other showing no effect or negative effects. Because of apparently universal reactivity with HIV strains, MBL clearly represents an important mechanism for recognition of HIV by the immune system. However, further studies are needed to define the in vivo contribution of MBL to clearance and destruction of HIV, the reasons for low neutralization by MBL and ways that MBL anti-viral effects can be augmented.     

Molecular genetic analysis of porcine mannose-binding lectin genes, MBL1 and MBL2, and their association with complement activity

Mannose-binding lectin (MBL) mediates activation of the complement system via the lectin pathway. Two forms of MBL, MBL-A and MBL-C, were characterized in rodents, rabbits, bovine and rhesus monkeys, whereas only one form was identified in humans, chimpanzees and chickens. The two forms are encoded by two distinct genes named MBL1 and MBL2, which have been identified in many species including the pig. In this report, we studied the two porcine genes MBL1 and MBL2. The porcine MBL genes had higher identities to bovine rather than primate and rodent sequences. Both genes were assigned to chromosome 14 by radiation hybrid panel and linkage mapping. Both MBL genes were highly expressed in liver. MBL1 was also found to be expressed in the lung, testis and brain, whereas low expression of MBL2 was detected in the testis and kidney. New single nucleotide polymorphisms of porcine MBL2 gene were found and genotyped in an experimental F2 pig population, together with a previously reported SNP of MBL1. MBL1 genotypes differed in C3c serum concentration, i.e. in vivo complement activity, at P < 0.1. Correspondingly, linkage analysis revealed a quantitative trait locus for C3c serum level close to the position of the MBL genes. The study thus promotes the porcine MBL genes as functional and positional candidate gene for complement activity.     

Analysis of the relationship between mannose-binding lectin (MBL) genotype,MBL levels and function in an Australian blood donor population

The mannose-binding lectin (MBL) pathway of complement activation is an important component of innate host defence. Numerous studies have described associations between the MBL genotype, MBL levels and disease susceptibility. However, genotyping and quantitative assays used in these studies have frequently been limited, and comprehensive data examining the interaction between structural and coding MBL genetic variants, MBL antigenic levels and MBL functional activity are lacking. Such data may be important for accurate planning and interpretation of studies of MBL and disease. This study has examined MBL in a cohort of 236 Australian blood donors. Five MBL promoter and coding single nucleotide polymorphisms were genotyped using polymerase chain reaction-sequence-specific priming (PCR-SSP). Plasma levels of MBL antigen were quantified using a double-antibody enzyme-linked immunosorbent assay (ELISA), and functional MBL levels were quantified using a mannan-binding assay. Activation of the complement pathway by MBL was measured in a C4-deposition assay. Significant associations were found between both coding and promoter polymorphisms and MBL antigenic and functional levels. There was significant correlation between the results of MBL double-antibody, mannan-binding and C4-deposition assays. Comprehensive MBL genotyping and functional MBL quantitation using mannan-binding and C4-deposition assays have the potential to be highly informative in MBL disease association studies.     

Significantly increased levels of mannose-binding lectin (MBL) in rheumatic heart disease: a beneficial role for MBL deficiency

Although mannose-binding lectin (MBL) is known to be involved in the primary defense against microorganisms, there are emerging lines of evidence for an active proinflammatory role for MBL in different chronic diseases. In this study we determined the circulating levels of MBL in patients with rheumatic heart disease (RHD). A total of 100 patients (77 women, 23 men; mean age 45.8 +/- 11 years, range 19-76 years) with chronic RHD, and a previous diagnosis of rheumatic fever, were studied. Transthoracic echocardiography was performed in all patients to evaluate valvular heart disease. Ninety-nine healthy individuals matched for age, sex and ethnic origin were included as controls. MBL concentration was measured by enzyme-linked immunosorbent assay and C3 and C4 levels by turbidimetry. MBL levels were significantly higher in patients with RHD than in healthy subjects (mean +/- SEM: 3036.2 +/- 298.9 ng/ml versus 1942.6 +/- 185.5 ng/ml, P <0.003). In addition, MBL deficiency was more prevalent in controls (17.1%) than in patients (9% P <0.09). Concentrations of C4 were within the normal range (22.7 +/- 0.8 mg/dl, normal: 10.0-40.0 mg/dl), while C3 concentrations were found to be elevated (109.2 +/- 3.6 mg/dl, normal: 50.0-90.0 mg/dl). No correlation was observed between serum MBL levels and valve area or the type of surgical procedure. The significantly elevated circulating MBL levels in patients with RHD together with the greater prevalence of MBL deficiency in controls suggest that MBL may cause undesirable complement activation contributing to the pathogenesis of RHD.