AIM: To observe whether pancreatic and duodenal homeobox factor-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells in vitro. METHODS: Rat pancreatic tissue was submitted ...AIM: To observe whether pancreatic and duodenal homeobox factor-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells in vitro. METHODS: Rat pancreatic tissue was submitted to digestion by collegenase, ductal epithelial cells were separated by density gradient centrifugation and then cultured in RPMI1640 medium with 10% fetal bovine serum. After 3-5 passages, the cells were incubated in a six-well plate for 24 h before transfection of recombination plasmid XlHbox8VP16. Lightcycler quantitative real-time RT-PCR was used to detect the expression of PDX-1 and insulin mRNA in pancreatic epithelial cells. The expression of PDX-1 and insulin protein was analyzed by Western blotting. Insulin secretion was detected by radioimmunoassay. Insulin- producing cells were detected by dithizone-staining. RESULTS: XlHbox8 mRNA was expressed in pancreatic ductal epithelial cells. PDX-1 and insulin mRNA as well as PDX-1 and insulin protein were signifi cantly increased in the transfected group. The production and insulin secretion of insulin-producing cells differentiated from pancreatic ductal epithelial cells were higher than those of the untransfected cells in vitro with a significant difference (1.32 ± 0.43 vs 3.48 ± 0.81, P < 0.01 at 5.6 mmol/L; 4.86 ± 1.15 vs 10.25 ± 1.32, P < 0.01 at 16.7 mmol/L). CONCLUSION: PDX-1 can differentiate rat pancreaticductal epithelial cells into insulin-producing cells in vitro. In vitro PDX-1 transfection is a valuable strategy for increasing the source of insulin-producing cells.展开更多
Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encod...Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encodes a methylation maintenance enzyme, is a transcriptional target of BRCA1. BRCA1 binds to the promoter of the DNMT1 gene through a potential OCT1 site and the binding is required for maintaining a transcriptional active configuration of the promoter in both mouse and human cells. We further demonstrated that impaired function of BRCA1 leads to global DNA hypomethylation, loss of genomic imprinting, and an open chromatin configuration in several types of tissues examined in a BRCA1 mutant mouse model at premaligant stages. BRCA1 deficiency is also associated with significantly increased expression levels of several protooncogenes, including c-Fos, Ha-Ras, and c-Myc, with a higher expression in tumors, while premalignant mammary epithelial cells displayed an intermediate state between tumors and controls. In human clinical samples, reduced expression of BRCA1 correlates with decreased levels of DNMT1, and reduced methylation of CpG islands. Thus, BRCA1 prevents global DNA hypomethylation through positively regulating DNMT1 expression, and this provides one of mechanisms for BRCAl-associated breast cancer formation.展开更多
The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of co...The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.展开更多
基金the grants from the National Natural Science Foundation of China, No.30571817the PhD Programs Foundation of Ministry of Education of China, No.20050487077
文摘AIM: To observe whether pancreatic and duodenal homeobox factor-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells in vitro. METHODS: Rat pancreatic tissue was submitted to digestion by collegenase, ductal epithelial cells were separated by density gradient centrifugation and then cultured in RPMI1640 medium with 10% fetal bovine serum. After 3-5 passages, the cells were incubated in a six-well plate for 24 h before transfection of recombination plasmid XlHbox8VP16. Lightcycler quantitative real-time RT-PCR was used to detect the expression of PDX-1 and insulin mRNA in pancreatic epithelial cells. The expression of PDX-1 and insulin protein was analyzed by Western blotting. Insulin secretion was detected by radioimmunoassay. Insulin- producing cells were detected by dithizone-staining. RESULTS: XlHbox8 mRNA was expressed in pancreatic ductal epithelial cells. PDX-1 and insulin mRNA as well as PDX-1 and insulin protein were signifi cantly increased in the transfected group. The production and insulin secretion of insulin-producing cells differentiated from pancreatic ductal epithelial cells were higher than those of the untransfected cells in vitro with a significant difference (1.32 ± 0.43 vs 3.48 ± 0.81, P < 0.01 at 5.6 mmol/L; 4.86 ± 1.15 vs 10.25 ± 1.32, P < 0.01 at 16.7 mmol/L). CONCLUSION: PDX-1 can differentiate rat pancreaticductal epithelial cells into insulin-producing cells in vitro. In vitro PDX-1 transfection is a valuable strategy for increasing the source of insulin-producing cells.
文摘Global DNA hypomethylation at CpG islands coupled with local hypermethylation is a hallmark for breast cancer, yet the mechanism underlying this change remains elusive. In this study, we showed that DNMT1, which encodes a methylation maintenance enzyme, is a transcriptional target of BRCA1. BRCA1 binds to the promoter of the DNMT1 gene through a potential OCT1 site and the binding is required for maintaining a transcriptional active configuration of the promoter in both mouse and human cells. We further demonstrated that impaired function of BRCA1 leads to global DNA hypomethylation, loss of genomic imprinting, and an open chromatin configuration in several types of tissues examined in a BRCA1 mutant mouse model at premaligant stages. BRCA1 deficiency is also associated with significantly increased expression levels of several protooncogenes, including c-Fos, Ha-Ras, and c-Myc, with a higher expression in tumors, while premalignant mammary epithelial cells displayed an intermediate state between tumors and controls. In human clinical samples, reduced expression of BRCA1 correlates with decreased levels of DNMT1, and reduced methylation of CpG islands. Thus, BRCA1 prevents global DNA hypomethylation through positively regulating DNMT1 expression, and this provides one of mechanisms for BRCAl-associated breast cancer formation.
基金supported by the National Basic Research Program of China (973 Program 2010CB428901)the National Natural Science Foundation of China (Grant Nos.41020164005,41221004)the ‘111’ Project
文摘The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.
