Project description:Rodent models are widely used to study diabetes. Yet, significant gaps remain in our understanding of mouse islet physiology. We generated comprehensive transcriptomes of mouse delta, beta and alpha cells using two separate triple transgenic mouse models generated for this purpose. This enables systematic comparison across thousands of genes between the three major endocrine cell types of the islets of Langerhans whose principal hormones control nutrient homeostasis. FACS purified delta or alpha cells and beta cells from the same islets. Islets were isolated from triple transgenic offspring of a cross between mIns1-H2b-mCherry (Jax # 028589) and either Sst-Cre (delta) or Gcg-cre (alpha) cells and a floxed YFP allele to label delta or alpha cells, respectively. Islets from replicate groups of 10 to 12 triple transgenic animals for each group were pooled by sex to obtain sufficient material. Pooled islets were dissociated, sorted and collect in Trizol for RNA isolation and library construction.
Project description:This study aimed to evaluate the efficacy of a purification method developed for isolating alpha, beta, and delta cells from pancreatic islets of adult mice, extending its application to islets from newborn and aged mice. Furthermore, it sought to examine transcriptome dynamics in mouse pancreatic endocrine islet cells throughout postnatal development and to evaluate age-related alterations in intercellular communication within these cell populations. We leveraged the high surface expression of CD71 on beta cells and CD24 on delta cells to FACS-purify alpha, beta, and delta cells from newborn (1-week-old), adult (12-week-old), and old (18-month-old) mice. Bulk RNA sequencing was conducted on these purified cell populations, and subsequent bioinformatic analyses included differential gene expression, overrepresentation, intersection, and intercellular communication analysis. Alpha, beta, and delta cells from newborn and aged mice were successfully FACS-purified using the same method employed for adult mice. Our analysis of the age-related transcriptional changes in alpha, beta, and delta cell populations revealed a decrease in cell cycling and an increase in so-called “neurogenesis” processes during the transition from newborn to adult mice. Progressing from adult to old mice, we observed an increase in β-2 microglobulin and major histocompatibility complex (MHC) Class I expression. Computational modeling of cell interactions suggested shifts in TGFβ and BMP signaling underpinning these age-related changes. Our study demonstrates the effectiveness of our cell sorting technique in purifying endocrine subsets from mouse islets at different ages. We provide a valuable resource for better understanding endocrine pancreas aging and identified increased β-2 microglobulin and MHC Class I expression as a common hallmark of old alpha, beta, and delta cells, with potential implications for immune response regulation.
Project description:High throughput sequencing has enabled the interrogation of the transcriptomic landscape of glucagon-secreting alpha cells, insulin-secreting beta cells, and somatostatin-secreting delta cells. These approaches have furthered our understanding of expression patterns that define healthy or diseased islet cell types and helped explicate some of the intricacies between major islet cell crosstalk and glucose regulation. All three endocrine cell types derive from a common pancreatic progenitor, yet alpha and beta cells have partially opposing functions, and delta cells modulate and control insulin and glucagon release. While gene signatures that define and maintain cellular identity have been widely explored, the underlying epigenetic components are incompletely characterized and understood. Chromatin accessibility and remodeling is a dynamic attribute that plays a critical role to determine and maintain cellular identity. Here, we compare and contrast the chromatin landscape between mouse alpha, beta, and delta cells using ATAC-Seq to evaluate the significant differences in chromatin accessibility. The similarities and differences in chromatin accessibility between these related islet endocrine cells help define their fate in support of their distinct functional roles. We identify patterns that suggest that both alpha and delta cells are poised, but repressed, from becoming beta-like. We also identify patterns in differentially enriched chromatin that have transcription factor motifs preferentially associated with different regions of the genome. Finally, we identify and visualize both novel and previously discovered common endocrine- and cell specific- enhancer regions across differentially enriched chromatin.
Project description:While immune checkpoint blockade therapy (ICBT) benefits cancer patients, many fail to maintain their response due to adaptive resistance mechanisms. IFNγ is critical for cellular immunity, but also promotes adaptive resistance to ICBT. We have established a role for PARP14 in mediating IFNγ-induced adaptive resistance. We confirm that chronic pre-treatment of tumour cells with IFNγ confers resistance to α-PD-1 antibodies in syngeneic mouse tumour models. We identified that PARP14 was consistently upregulated in cancer cells treated chronically with IFNγ as well as in IFNγ-high melanoma samples. Further, we showed that PARP14 knockdown or pharmacological inhibition restores sensitivity to α-PD-1 antibodies accompanied by increased immune cell infiltration into tumours but the decreased presence of regulatory T cells. RNA sequencing analysis of tumours and cultured cells treated with PARP14 inhibitor showed an upregulation of inflammatory-related pathways. In conclusion, PARP14 is an actionable target for reversing IFNγ-driven adaptive resistance to ICBT.
Project description:While immune checkpoint blockade therapy (ICBT) benefits cancer patients, many fail to maintain their response due to adaptive resistance mechanisms. IFNγ is critical for cellular immunity, but also promotes adaptive resistance to ICBT. We have established a role for PARP14 in mediating IFNγ-induced adaptive resistance. We confirm that chronic pre-treatment of tumour cells with IFNγ confers resistance to α-PD-1 antibodies in syngeneic mouse tumour models. We identified that PARP14 was consistently upregulated in cancer cells treated chronically with IFNγ as well as in IFNγ-high melanoma samples. Further, we showed that PARP14 knockdown or pharmacological inhibition restores sensitivity to α-PD-1 antibodies accompanied by increased immune cell infiltration into tumours but the decreased presence of regulatory T cells. RNA sequencing analysis of tumours and cultured cells treated with PARP14 inhibitor showed an upregulation of inflammatory-related pathways. In conclusion, PARP14 is an actionable target for reversing IFNγ-driven adaptive resistance to ICBT.
Project description:Intra-islet crosstalk between islet cells is critical in orchestrating the body’s response to changes in blood glucose levels, but is incompletely understood. In this study, we used transgenic mouse lines that allowed the purification and transcriptomic characterisation of alpha, beta, and delta cells, yielding an RNA-sequencing database that can be searched for regulatory proteins which are differentially expressed between cell types. As an illustrative example, we examined the expression of g-protein coupled receptors, and found that the ghrelin receptor, Ghsr, was highly expressed in delta cells compared to alpha and beta cells. GHSR excitation elicited increases in cytosolic calcium levels in primary delta cells. In the perfused pancreas, the application of ghrelin stimulated somatostatin secretion, correlating with a decrease in insulin and glucagon release, which was sensitive to somatostatin receptor antagonism. These results show that ghrelin acts specifically on delta cells within pancreatic islets to affect blood glucose regulation.
Project description:While immune checkpoint blockade therapy (ICBT) benefits cancer patients, many fail to maintain their response due to adaptive resistance mechanisms. IFNγ is critical for cellular immunity, but also promotes adaptive resistance to ICBT. We have established a role for PARP14 in mediating IFNγ-induced adaptive resistance. We confirm that chronic pre-treatment of tumour cells with IFNγ confers resistance to α-PD-1 antibodies in syngeneic mouse tumour models. We identified that PARP14 was consistently upregulated in cancer cells treated chronically with IFNγ as well as in IFNγ-high melanoma samples. Further, we showed that PARP14 knockdown or pharmacological inhibition restores sensitivity to α-PD-1 antibodies accompanied by increased immune cell infiltration into tumours but the decreased presence of regulatory T cells. RNA sequencing analysis of tumours and cultured cells treated with PARP14 inhibitor showed an upregulation of inflammatory-related pathways. In conclusion, PARP14 is an actionable target for reversing IFNγ-driven adaptive resistance to ICBT.
Project description:Rodent models are widely used to study diabetes. Yet, significant gaps remain in our understanding of mouse islet physiology. We generated comprehensive transcriptomes of mouse delta, beta and alpha cells using two separate triple transgenic mouse models generated for this purpose. This enables systematic comparison across thousands of genes between the three major endocrine cell types of the islets of Langerhans whose principal hormones control nutrient homeostasis.