RÉSUMÉ
AIM: To investigate the role of epigenetic modification in Pdx-1 gene transcription and expression, and to compare the differences between epigenetic modifications of Pdx-1 gene promoter in various cell types of mice. METHODS: The promoter DNA methylation and histone modification status of Pdx-1 and MLH1 genes in NIT-1 cells, NIH3T3 cells and mouse embryonic stem cells were measured by chromatin immunoprecipitation-real time PCR method. The expression levels of these genes in the three cell lines were measured by real time RT-PCR. The relation between epigenetic modifications and gene expression was analyzed. RESULTS: (1) Compared to mES cells, there was lower DNA methylation and higher H3K4m3 modification levels in the promoter of Pdx-1 gene in NIT-1 cells (P<0.05). DNA methylation, H3 acetylation, H3K4m3 and H3K9m3 modification levels in the promoter of Pdx-1 gene in NIH3T3 cells were distinctly increased (P<0.05). (2) Pdx-1 gene transcription expressed only in NIT-1 cells. The Spearman's rho between Pdx-1 gene expression and DNA methylation (r=-0.802,P<0.01) was observed. The Pearson correlation between Pdx-1 gene expression and H3K4m3 modification (r=0.997,P<0.01) was also found. The Spearman's rho between Pdx-1 gene expression and H3K9m3 modification (r=-0.879,P<0.01) was observed. (3) No correlation between housekeeper MLH1 gene expression and epigenetic modification was found. CONCLUSION: DNA methylation, H3K4m3 and H3K9m3 modification coordinated participate to regulate and control the expression of Pdx-1 gene. It is of great significance to the differentiation of β cells from ES cells.
RÉSUMÉ
AIM: To clone mouse pdx-1 gene and construct its eukaryotic expression vector for expression of pdx-1 in mouse embryonic stem cells.METHODS: Mouse pdx-1 cDNA fragment was amplified with polymerase chain reaction (PCR) from mouse pancreatic cDNA. The purified fragment was recombinated with a eukaryotic expression vector carrying enhanced green fluorescent protein, pEGFP-N1. The pdx-1 cDNA fragment was inserted into the multi-clone sites of the vector to construct a new plasmid, pEGFP/pdx-1. E.colli strain DH5? was transfected with the new recombinant plasmid to expand it. Plasmid DNA extracted from the expanded DH5? was identifed by cutting with Hind Ⅲ, BamHⅠ nuclease and by DNA sequencing. Identified plasmid DNA was transfected into mouse embryonic stem cell line MESPU13 by carrying with liposome. RESULTS: A 876 bp cDNA fragment was amplified from mouse pancreatic cDNA by PCR and it was inserted into the vector pEGFP-N1 correctly. The fragment was defined to be pdx-1 gene by nuclease digestion and DNA sequencing. Mouse embryonic stem cell line MESPU13 was transfected with the new recombinant plasmid DNA. The green fluorescent protein report gene and pdx-1 gene expressed in transfected mouse embryonic stem cells within 24 h. CONCLUSION: Mouse pdx-1 gene is cloned and its recombinant eukaryotic expression vector carrying green fluorescent protein is constructed successfully. It provides a useful tool for further research on the function of pdx-1.