BioProject

Expression of the proendocrine gene neurogenin 3 (Ngn3) is required for the development of pancreatic islets. In order to better characterize the molecular events regulated by Ngn3 during development, we have determined the expression profile of differentiating murine embryonic stem cells (mESCs) uniformly induced to overexpress Ngn3. An ESC line was created that allows for the induction of Ngn3 by adding doxycycline (Dox) to the culture medium. Genome-wide microarray analysis was performed to identify genes regulated by Ngn3 in a variety of both undifferentiated and differentiated conditions. Characterization of pancreatic developmental markers during embryoid body (EB) formation revealed an optimum context for Ngn3 induction. Neuroendocrine genes including neurogenic differentiation 1 (NeuroD1) and single minded 1 (Sim1) were found to be significantly upregulated. Genes regulated by Ngn3 independent of the context were analyzed using systematic gene ontology tools and revealed Notch signaling as the most significantly regulated signaling pathway (p=0.009). This result is consistent with the hypothesis that Ngn3 expression makes the cell competent for Notch signaling to be activated and conversely, more sensitive to Notch signaling inhibition. Indeed, EBs induced to express Ngn3 were significantly more sensitive to gamma-secretase inhibitor-mediated Notch signaling inhibition (p<0.0001). Moreover, we find that Ngn3 induction in differentiating ESCs results in significant increases in insulin, glucagon, and somatostatin transcription. Keywords: Ngn3 induction, embryonic stem cell differentiation Overall design: 16 embryonic stem cell (ESC) samples (8 groups in duplicate) were processed for microarray analysis using the Affymetrix Mouse Genome 430 2.0 GeneChip. The samples included the parental Ainv15 ESC line (1) undifferentiated (Ainv15 ESC), (2) differentiated for 3 days as embryoid bodies (Ainv15 EB3) or (3) for 10 days as embryoid bodies (Ainv15 EB10). The remaining samples included tetracycline inducible Ngn3 ESC line derived from the parental Ainv15 ESC line (4) after differentiation and addition of doxycycline for 3 days without embryoid body formation (Ngn3 ES3 ON), (5 and 6) after differentiation as embryoid bodies for 3 days with (Ngn3 EB3 ON) or without (Ngn3 EB3 OFF) doxycycline, and (7 and 8) after differentiation as embryoid bodies for 10 days with (Ngn3 EB10 ON) or without (Ngn3 EB10 OFF) doxycycline.