Expression Of Aspartylglucosaminidase And Sorting Nexins17 At Transcriptional Levels In Thymic Tissue Of MG

Background and ObjectiveMyasthenia gravis (MG) is one of autoimmune diseases caused by acetylcholine receptor antibodies (AchRAb), whose targets are the acetylcholine receptors (AchR) on the postsynaptic membrane at the neuromuscular junction (NMJ). Recent years, a lot of studies have been done about the pathogenesis of MG, confirming the important function, of immunologic mechanisms in the morbidity process. In addition, genetic predisposition and liability was also detected in the morbidity of MG, which is associated with HLA phenotype, AchR a subunit gene, immunoglobulin H chain gene and TCR gene. Many studies have demonstrated that MG is associated with pathological alterations of the thymus in 80%-90% of the cases and the clinical symptoms are relieved in most of MG patients after thymectomy. Our team of MG research discovered 25 high expression genes of MG with the gene chip tech and Lib of differential display in the thymic tissue of MG. Aspartylglucosaminidase (AGA) and sorting nexins17 (SNX17) genes are associated with the pathogenesis of MG among these genes. But, there are not related reports about the relationship of AGA and SNX17 genes with MG.AGA is a key enzyme in the catabolism of glycoproteins into N-linked oligosaccharides. It can cleave the asparagine from the residual N-acetylglucosamines, and this is one of the final steps in the lysosomal breakdown of glycoproteins. Morris et al. found the gene at 4q32-q33 by in situ hybridization. SNX17 constitutes a large conserved family of hydrophilic molecules that interact with various types of receptors. The International Radiation Hybrid Mapping Consortium mapped the SNX17 gene at chromosome 2 (2p23-p22). SNX17 has been identified as a novel interaction partner for members of the LDLR family. It resides in distinct parts of the early endosomal compartment and enhances the endocytosis rate of the LDLR, and possibly other surface receptors.We used Fluorescent Quantitative Polymerase Chain Reaction to analyse the expression of the AGA and SNX17 genes in MG thymic and normal tissues at transcriptional levels, presume the relativity between two genes and the maligenic mechanism of MG, and provide evidence for further basic reseaches and biological treatment.Materials and methodsConstruct and dilute the recombinant plasmid pGEM-T-B-actin, amplify it according to FQ-PCR reaction system and reaction condition, define the standard curve. Extract the total RNA from 39 thymic tissue samples of MG patients and 10 normal samples of patients who have congenital heart diseases and need operations. Then reverse transcription RNA to cDNA in the catalysis of avian myeloblastosis virus (AMV). According to FQ-PCR reaction system and reaction condition, amplify the genes of B-actin, AGA and SNX17, get the Ct value of them. The Ct value ratio of AGA and P-actin could be seen as the relative expression amount of AGA gene at mRNA level, the Ct value ratio of SNX17 and B-actin can be seen as the relative expression amount of SNX17 gene at mRNA level, respectively. Contrast the expression of AGA and SNX17 genes at mRNA level between MG patients and the control group, male and female patients, and in different clinical classification of MG patients.Use the SPSS 10.0 software package to analysis these dates with two-sample t-test for independent samples or analysis of variance (ANOVA),α=0.05. Results(1) The expression of AGA mRNA in the thymic tissues of MG was 0.67±0.14. It was significantly higher than the expression in the control group, which was 0.61±0.08 (P<0.05). The expressions in different clinical classificition of MG thymic tissues were 0.66±0.14, 0.63±0.13, 0.70±0.09 and 0.71±0.16, respectively, which was no significant difference (P>0.05).(2) The expression of SNX17 mRNA in the thymic tissues of MG was 0.70±0.11. It was significantly higher than the expression in the control group, which was 0.62±0.13 (P<0.05). The expressions in different clinical classificition of MG thymic tissues were 0.67±0.16, 0.69±0.06, 0.71±0.08 and 0.75±0.18, respectively, which was no significant difference (P>0.05).(3) The expression of AGA gene at mRNA level in male and female patients of MG was 0.64±0.15 and 0.69±0.13, respectively, which was no significant difference (P>0.05). The expression of SNX17 gene at mRNA level in male and female patients of MG was 0.67±0.21 and 0.71±0.11, which was no significant difference (P>0.05).Conclusions(1) AGA gene with the high expression at mRNA level in the thymic tissues of MG is associated with the pathogenesis of MG. It is abnormality expression at transcriptional level.(2) SNX17 gene with the high expression at mRNA level in the thymic tissues of MG is associated with the pathogenesis of MG. It is abnormality expression at transcriptional level.(3) AGA and SNX17 genes are not associated with pathogenetic condition and obviously different between male and female MG patients.