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Bulk RNA-seq in pancreatic islets of Tg7 mice

ABSTRACT: Objective: beta-cell dedifferentiation has been revealed as a pathological mechanism underlying pancreatic dysfunction in diabetes. However, exactly how such dedifferentiation process affects beta-cell gene expression and islet microenvironment remains incompletely understood Method: We performed bulk in islets obtained from beta-cell-specific miR-7a2 overexpressing mice (Tg7), a murine model of beta-cell dedifferentiation and diabetes. Results: Bulk RNA-seq revealed that beta-cell dedifferentiation is associated with the induction of genes associated with epithelial to mesenchymal transition (EMT) in pre-diabetic (2-week-old) and diabetic (12-week-old) Tg7mice. These molecular changes are associated with a weakening of beta-cell:beta-cell contacts, increased extracellular matrix (ECM) deposition and TGFb-dependent islet fibrosis. We find that the mesenchymal reprogramming of beta-cells is explained in part by the downregulation of Pdx1 and its inability to regulate a myriad of target genes preserving the epithelial cell phenotype. Notable among epithelial genes transactivated by Pdx1 is Ovol2, a transcriptional repressor of the EMT transcription factor ZEB2. Following compromised beta-cell identity, the reduction of Pdx1 mRNA levels decreases Ovol2 gene expression, which triggers mesenchymal reprogramming of beta-cells through the induction of Zeb2. Finally, we provided evidence that EMT signalling associated with the upregulation of Zeb2 expression is a molecular feature of islet of T2D subjects. Conclusions: Our study indicates that beta-cell dedifferentiation triggers a chronic response to tissue injury, which alters the pancreatic islet microenvironment and contribute to islet fibrosis. It suggests that regulators of EMT signalling may represent novel therapeutic targets for the treatment of beta-cell dysfunction and fibrosis in T2D.

ORGANISM(S): Mus musculus

PROVIDER: GSE171251 | GEO | 2021/07/21

REPOSITORIES: GEO

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Project description:Recent advances in the understanding of the genetics of type 2 diabetes (T2D) susceptibility have focused attention on the regulation of transcriptional activity within the pancreatic beta-cell. MicroRNAs (miRNAs) represent an important component of regulatory control, and have proven roles in the development of human disease and control of glucose homeostasis. We set out to establish the miRNA profile of human pancreatic islets and of enriched beta-cell populations, and to explore their potential involvement in T2D susceptibility. We used Illumina small RNA sequencing to profile the miRNA fraction in three preparations each of primary human islets and of enriched beta-cells generated by fluorescence-activated cell sorting. In total, 366 miRNAs were found to be expressed (i.e. >100 cumulative reads) in islets and 346 in beta-cells; of the total of 384 unique miRNAs, 328 were shared. A comparison of the islet-cell miRNA profile with those of 15 other human tissues identified 40 miRNAs predominantly expressed (i.e. >50% of all reads seen across the tissues) in islets. Several highly-expressed islet miRNAs, such as miR-375, have established roles in the regulation of islet function, but others (e.g. miR-27b-3p, miR-192-5p) have not previously been described in the context of islet biology. As a first step towards exploring the role of islet-expressed miRNAs and their predicted mRNA targets in T2D pathogenesis, we looked at published T2D association signals across these sites. We found evidence that predicted mRNA targets of islet-expressed miRNAs were globally enriched for signals of T2D association (p-values <0.01, q-values <0.1). At six loci with genome-wide evidence for T2D association (AP3S2, KCNK16, NOTCH2, SCL30A8, VPS26A, and WFS1) predicted mRNA target sites for islet-expressed miRNAs overlapped potentially causal variants. In conclusion, we have described the miRNA profile of human islets and beta-cells and provide evidence linking islet miRNAs to T2D pathogenesis. Examination of the miRNA profiles in 3 preparations of isolated pancreatic islets and 3 preparations of FACS-enriched pancreatic beta-cells

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Bulk RNA-seq in pancreatic islets of Tg7 mice

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