| Objective ACAT1, encoded by Soat1gene, plays an important role in maintaining the dynamic equilibrium of intracellular cholesterol, directly or indirectly affect the secretion of APP and the production of Aβ. COX, encoded by Ptgs2gene, can metabolize arachidonic acid to various prostaglandins, in which, PGE was involved in the synthesis and transport of cholesterol. Overexpression of Ptgs2can induce the neural degenerative diseases by the enhancive excitotoxicity of Aβ. Thus, we conjecture that there is a relationship between Ptgs2gene and Soatl gene in the transport and transformation of intracellular cholesterol, then they may jointly take part in the pathogenesis of Alzheimer’s disease (AD). In order to investigate the synergistic molecular mechanism of Soat1gene and Ptsg2gene in the pathogenesis of AD, we carried out microarray analysis, expression quantitative trait loci (eQTL) and genetic correlation analysis to construct the expression regulation network of Soatl gene and Ptgs2gene by using the BXD recombinant inbred (RI) mice. Methods Microarray analysis was carried out to evaluate the expression variation of Soat1and Ptgs2gene in the hippocampus of the BXD RI mice and parent strains (C57BL/6J and DBA/2). Interval mapping was performed to define the chromosome regions associated with expression differences for Soatl gene and Ptgs2gene by using the BXD recombinant inbred mice. In order to detect whether the single nucleotide polymorphism (SNPs) could influence eQTL mapping, we collected the SNPs between B6strains and D2strains, then carried out the multiple mapping probe by probe. Using Cluster Map online analysis tools, identify the gene which was trans-regulated by the Soatl gene and Ptgs2gene in the hippocampus of the BXD RI mice, which were predicted to be the candidate downstream genes of the Soatl gene and Ptgs2gene. Construct genetic regulatory network of the gene by using Pearson Correlation analysis.Results The result of RT-PCR showed that there are significant expression differences of Soatl gene between B6and D2. The expression of B6is higher than the expression of D2. The average value of the expression of Soatl in the hippocampus of the BXD RI mice is7.959(more than7). Further more, the expression variance of Soatl in BXD RI mice performed a linear trend. The eQTL mapping for Soatl gene showed that the locus had significant linkage scores (LRS) of89.2. Furthermore, this QTL region was located within5Mb of Soatl gene itself, and so was indicative of a cis acting QTL. Using the Cluster Map online analysis tool, we identified a trans-QTL band which was trans-activated by the Soatl gene. The trans-QTL band included21genes. Ruled out the influence of the linkage disequilibrium on the downstream gene localization, results indicate that the7genes of them showing significant partial correlation with Soatl. It is speculated that the7genes are the downstream regulative candidate genes of the Soatl gene. Make analyze of the genetic correlation of the Soatl gene and the other genes of the hippocampus of the BXD recombinant inbred mice by the Pearson correlation, select18genes with high genetic correlation (more than0.43) to construct genetic gene network. Ptgs2gene was contained in them with genetic correlation as high as0.61.High expression of Ptgs2in the hippocampus of the BXD RI mice has been detected. The average value of the expression is more than8.32. The value of B6is8.54. The value of D2is low, at7.86. The difference between the two parents has reached to1.6times, and the difference was statistically significant. The changes among the expression of the the various strains of BXD RI are on a linear trend, corresponding in the quantitative trait. Gene expression quantitative traits loci analysis found that control of the eQTL of Ptgs2gene is cis-eQTL. That is Gene expression changes controls by itself. Ptgs2cis-eQTL was predicted to be a hotspot of trans-eQTL by cluster mapping. Eight genes within this region were suggested to be the potential downstream targets of Ptgs2by the Partial correlation analysis. Pearson correlation analysis revealed that there were151probe sets exhibit high correlations with Ptgs2. The r value of the top13correlations were higher than0.59. Soat1gene was contained in them.In the genetic network of Ptgs2gene and Soat1gene, ten genes among them have a high correlation with Soat1gene and Ptgs2gene. Among them, Dnm3gene and Glul gene were involved in the incidence of AD. Dnm3, a member of Dnm family, involved in the cholesterol distribution and metabolism. Thus, we conjecture that Soatl gene is connected by Dnm and Glul gene to Ptgs2gene and they jointly participate in the pathogenesis of AD. These results further show that Soatl gene and Ptgs2gene were collaborative involved in the pathogenesis of AD. Conclusions The preliminary conclusion of this experiment is that the Soat1gene and the Ptgs2genes are cis-acting regulated genes. The7genes including Rab2gene and Taz gene are the candidated downstream genes regulated by Soatl gene. The8genes including Vcam1gene and Mlstd1gene are the candidated downstream genes regulated by Ptgs2gene. A significant high correlation between Ptgs2and Soatl has been showed both in the gene networks of Soat1gene and Ptgs2gene. In the gene networks of Ptgs2gene and Soat1gene, Dnm and Glul gene with Soatl and Ptgs2show a high correlation. Both of them were involved in APP processing and the production of Aβ. Thus, we conjecture that Soatl gene is connected to Ptgs2gene by Dnm gene and Glul gene, and they jointly participate in the pathogenesis of AD. This further proved that Ptgs2gene and Soatl gene were collaborative involved in the pathogenesis of AD. |
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