Apoptosis following activation of MYC-ERTAM. A) Sections from 4OHT-treated MYC-ERTAM transgenic mice were stained with Caspase 3-specific antibodies (green) and a tissue specific antibody (red; insulin for β-cells, keratin 1 for SBK). DAPI staining (blue) identifies cell nuclei. No Caspase 3 staining was detected in β-cells or SBK in vehicle-treated (VT) samples. Following 32 hours of 4OHT, Caspase 3 was detected in β-cells, but no Caspase 3 activity was detected in treated SBK indicating that apoptosis is specific to the β-cell model. Images shown are representative sections from different levels through replicate tissue samples. b, basal keratinocyte; sb, suprabasal keratinocyte. B) The change in expression of genes relating to apoptosis and cell survival following activation of MYC-ERTAM is represented as a heatmap (red, up-regulated; black, no change; green, down-regulated). C) qRT-PCR validation for gene expression changes in genes relating to apoptosis and cell survival confirms disparate changes in gene expression between skin and pancreas. Genes relating to DNA-damage in particular, such as Atr and Chk2, show a clear increase in expression for pancreatic β-cells, which confirms changes seen in microarray data, as did apoptosis genes Cycs and Endog. As with the microarray data, up-regulation of the Igf1 gene was detected from 8 hours for the skin following MYC-ERTAM activation, with an increase in expression also detected for the pancreas at the later 32 hour time point.