RESUMEN
We used mice lacking Abcc8, a key component of the ß-cell KATP-channel, to analyze the effects of a sustained elevation in the intracellular Ca2+ concentration ([Ca2+]i) on ß-cell identity and gene expression. Lineage tracing analysis revealed the conversion of ß-cells lacking Abcc8 into pancreatic polypeptide cells but not to α- or δ-cells. RNA-sequencing analysis of FACS-purified Abcc8-/- ß-cells confirmed an increase in Ppy gene expression and revealed altered expression of more than 4,200 genes, many of which are involved in Ca2+ signaling, the maintenance of ß-cell identity, and cell adhesion. The expression of S100a6 and S100a4, two highly upregulated genes, is closely correlated with membrane depolarization, suggesting their use as markers for an increase in [Ca2+]i Moreover, a bioinformatics analysis predicts that many of the dysregulated genes are regulated by common transcription factors, one of which, Ascl1, was confirmed to be directly controlled by Ca2+ influx in ß-cells. Interestingly, among the upregulated genes is Aldh1a3, a putative marker of ß-cell dedifferentiation, and other genes associated with ß-cell failure. Taken together, our results suggest that chronically elevated ß-cell [Ca2+]i in Abcc8-/- islets contributes to the alteration of ß-cell identity, islet cell numbers and morphology, and gene expression by disrupting a network of Ca2+-regulated genes.
