| Mannan-binding lectin (MBL) is one of members of the collectin(C-type lectin with a collagen-like domain) family in the superfamily of C-type lectins and is considered a key component of innate immunity. Upon recognizing and binding to certain carbohydrate moieties on various pathogens, it can mediate phagocytosis and use MBL serine proteases-1 and -2 to activate the MBL pathway of complement, cleaning potential pathogenic microorganisms and infected cells. However, the function of MBL depends on a certain levels of serum MBL and its oligomeric form. MBL deficiency and low levels of serum MBL are the basis for a common opsonic defect and are associated with recurrent infections with an increased susceptibility to various pathogens and the process of autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis(RA).MBL is synthesized in the liver and secreted into the bloodstream, the concentration of which is for the most part genetically determined by a series of allelic dimorphisms located both in the structural gene and in the promoter region. The different structural variants is the result of a single point mutation in exon 1 that disrupts the collagen-like structure of the MBL polypeptide or accelerates the MBL degradation which leads to a reduction of functional MBL in individuals. Complex promoter region have structure exon 0 and multiple regulating sequences containing seven single base variations(single nucleotide polymorphism, SNP) and a six-base deletion. Polymorphisms in the promoter and 5'untranslated region of the MBL gene located at nucleotides -550g/c (alleles H/L), -220c/g(X/Y) and +4c/t(P/Q) alse have a dramatic effect on serum MBL levels. Combination of various promoter genotypes regulating transcription of the MBL gene and the different structural gene variants are responsible for the large interracial and interindividual variations in MBL serum levels.China is a populous country with many nationalities, it is necessary to studythe genetic polymorphisms of MBL gene in Chinese so as to provide decision-making evidence for prevention and treatment of MBL deficiency. Therefore, the main SNPs haplotypes and genotypes in the promoter region of the MBL gene of 5 Chinese nationalities(Hans Uars Bais, Larhus and Mongolias) have been studied in present syudy. Objectives:1. To establish simple, inexpencive, rapid techniques to detect main SNPs of MBL gene with high sensitivity and specificity, which must be also adapted for analysis of haplotypes and genotypes.2. To define the distribution of the alleles, haplotypes and genotypes of main SNPs in MBL gene promoter region in Hans, Uars, Bais, Larhus and Mongolias by investigating the main SNPs with the techniques above.Materials and Methods:1. Blood samples of the populations of Hans, Uars, Baism Larhus and Mongolias were collected and genome DNA of white blood cells extracted.2. A sequence specific primers-polymerase chain reaction(SSP-PCR) system for detecting alleles H/L and P/Q and amplifying target sequence fragments containing alleles X/Y was established.3. A polymerase chain reaction-molecular beacon(PCR-MB) visual monitoring approach for identifying alleles X/Y was established, in which the fluorescence was viewed by illuminating the tubes with a broad-wavelength ultraviolet lamp.4. An automatic high-throughput real time-PCR-MB hybridization technique was established and used to detecting the alleles X/Y contained in the SSP-PCR products of MBL gene promoter region in the several populations.5. Combining the results of SSP-PCR and PCR-MB, the alleles, haplotypes and genotypes of main SNPs in the promoter region of the MBL gene were determined and their intertribal distribution differences analyzed.Results:1. Genome DNA of all samples was extracted by using erythrocyte lysis solution and PCR buffer/nonionic detergent/proteinase K, from which the target sequence fragments were amplified successfully.2. The alleles H/L and P/Q were detected using the established SSP-PC...
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