Quantification of Insulin Gene Expression During Development of Pancreatic Islet Cells

Objective: Despite great progress in understanding the transcriptional regulation of the development of insulin-secreting A cells, the quantitative temporal expression of insulin gene(s) remains largely unknown. We here aimed to quantify insulin gene transcripts during development. Methods: We described bioinformatics algorithms to quantify (insulin) gene transcript abundance in sequential microarray data sets at the global level. Several molecular techniques were used to confirm our analyses. Results: We demonstrated that the expression of insulin genes was up-regulated at approximately 14-fold, 700- to 2000-fold, and 5000- to 6000-fold in Pdx1- and Ngn3-expressing cells and adult islets compared with definitive endodermal or embryonic stem cells, respectively. The expression of multiple genes encoding molecules involved in posttranslational modi. cations of insulin and glucose sensing was also elevated in the same period. All islet and associated genes determined with microarray data were confirmed not only to be up-regulated by real-time quantitative reverse transcriptase polymerase chain reaction but also that the magnitude of their increase quantified with these 2 methods was statistically highly correlated. Consistent with the above, green fluorescence protein expression under the control of the mouse insulin 1 promoter could be visualized in the pancreas from embryonic day (E) 11.5, increasing progressively through E13.5 to E15.5. Conclusion: Our study provides a novel insight into islet developmental biology.