DDX1 regulates alternative splicing and insulin secretion in pancreatic β cells
Ontology highlight
ABSTRACT: DEAD-box helicase 1 (DDX1) is a multifunction protein involved in diverse cellular processes including transcription, viral replication, mRNA/miRNA processing, and tRNA splicing. Here, we report a novel function of DDX1 in mRNA alternative splicing in pancreatic β cells. By performing integrated data analysis of high-throughput RNA sequencing (RNA-Seq), and cross-linking and immunoprecipitation coupled with deep sequencing (CLIP-Seq), we identify hundreds of alternative splicing genes that are targeted by DDX1. These DDX1-targeted alternative splicing genes are mainly associated with calcium ion binding, high voltage-gated calcium channel, and transmembrane transporter. Functionally, silencing DDX1 impairs calcium influx and insulin secretion in the pancreatic β cells. These results reveal an important role for DDX1 in the regulation of gene alternative splicing and insulin secretion in pancreatic β cells.
Project description:Alternative splicing (AS) is a fundamental mechanism for the regulation of gene expression. It affects more than 90% of human genes but its role in the regulation of pancreatic beta cells, the producers of insulin, remains unknown. Our recently published data indicated that the M-bM-^@M-^\neuron specificM-bM-^@M-^] Nova1 splicing factor is expressed in pancreatic beta cells. We have presently coupled specific knockdown (KD) of Nova1 with RNA-sequencing to determine all splice variants and downstream pathways regulated by this protein in beta cells. Nova1 KD altered the splicing of nearly 5000 transcripts. Pathway analysis indicated that these genes are involved in exocytosis, apoptosis, insulin receptor signalling, splicing and transcription. In line with these findings, Nova1 silencing inhibited insulin secretion and induced apoptosis basally and after cytokine treatment in rodent and human beta cells. These observations identify a novel layer of regulation of beta cell function, namely AS controlled by key splicing regulators such as Nova1. 3 batch of primary rat pancreatic beta cells were examined under 2 conditions: control and with Nova1 splicing factor knock-down
Project description:We report the discovery of circadian clock-controlled alterantive pre-mRNA splicing in pancreatic beta cells and its role in insulin secretion. We performed RNA-sequencing in CRISPR-CAS9 edited Clock and Bmal1 knockout BetaTC6 cells and used differential mRNA expression and splicing analysis to identify and validate transcriptional and alternative splicing targets of the circadian clock regulating insulin secretion.
Project description:Activating mutations in the KATP channel cause a rare genetic form of diabetes called neonatal diabetes. These mutations render the channel permanently open results in membrane hyperpolarisation of the pancreatic beta-cell. This prevents calcium influx and impairs insulin secretion. Mice expressing the human neonatal diabetes mutation Kir6.2-V59M specifically in pancreatic beta-cells are diabetic but do not display dyslipidaemia or insulin resistance. In this experiment, gene expression changes were analysed to explore the effect of high blood glucose per se on isolated pancreatic islets
Project description:Alternative splicing (AS) is a fundamental mechanism for the regulation of gene expression. It affects more than 90% of human genes but its role in the regulation of pancreatic beta cells, the producers of insulin, remains unknown. Our recently published data indicated that the “neuron specific” Nova1 splicing factor is expressed in pancreatic beta cells. We have presently coupled specific knockdown (KD) of Nova1 with RNA-sequencing to determine all splice variants and downstream pathways regulated by this protein in beta cells. Nova1 KD altered the splicing of nearly 5000 transcripts. Pathway analysis indicated that these genes are involved in exocytosis, apoptosis, insulin receptor signalling, splicing and transcription. In line with these findings, Nova1 silencing inhibited insulin secretion and induced apoptosis basally and after cytokine treatment in rodent and human beta cells. These observations identify a novel layer of regulation of beta cell function, namely AS controlled by key splicing regulators such as Nova1.
Project description:Insulin secreted by pancreatic β cells is essential for maintaining the level of blood glucose. Diabetes is mainly caused by the loss of β cells or impaired β cell function. The previous study performed a whole transcriptome analysis on the islets of T2D and the control group, and the results showed that the splicing disorder of the splicing event was about 25%, breast carcinoma amplified sequence 2(BCAS2) is one of the components of the spliceosome, and its function in islet β cell is unclear. Here we report that knockdown of Bcas2 decreases in glucose and KCl-stimulated insulin secretion in the NIT-1 cell line. The pancreas weight, glucose tolerance and insulin sensitivity were detected in normal chow-fed and high-fat diet-fed Bcas2 f/f-βKO mice, and β cell mass and islet size was analyzed by immunohistochemistry. Glucose intolerance developed in Bcas2 f/f-βKO mice, but there were no significant differences in pancreas weight, insulin sensitivity, β cell mass and islet size. Further, GSIS and observation of insulin secretion granules were performed on normal chow-fed mice, and it was found that the insulin level in serum decreased and the number of insulin secretion granules decreased in Bcas2 f/f-βKO mice, which was related to the abnormal splicing of Syt7 and Tcf7l2 pre-mRNA. Taken together, these results demonstrate that BCAS2 is involved in alternative splicing during insulin synthesis and secretion. Elisa,islet isolation,insulin secretion
Project description:Previous studies have focused on the combined glucolipoxicity that is presence of high glucose and free fatty acid levels effect on insulin gene expression, but the effect of high FFA and normal glucose level on insulin expression is unkown. Here we observed that palmitate can inhibit insulin translation. And we identified a novel insulin mrna binding protein DDX1 that is responsible for fatty acid mediated insulin translation inhibition. Palmitate treatment causes phosphorylation of DDX1 at S295 and dissociation from insulin mRNA, which decreases insulin translation.
Project description:Insulin expression is restricted to the pancreatic beta cells, which are physically or functionally depleted in diabetes. Identifying targetable pathways repressing insulin in non-beta cells, particularly in the developmentally related glucagon-secreting alpha cells, is an important aim of regenerative medicine. Here, we performed an RNA interference screen in the murine alpha cell line, alphaTC1, to identify silencers of insulin expression. We discovered that knockdown of the splicing factor Smndc1 (Survival Motor Neuron Domain Containing 1) triggered a global repression of alpha cell gene-expression programs in favor of increased beta cell markers. Mechanistically, Smndc1 knockdown upregulated the key beta cell transcription factor Pdx1, by modulating the activities of the BAF and Atrx families of chromatin remodeling complexes. SMNDC1’s repressive role was conserved in human pancreatic islets, its loss triggering enhanced insulin secretion and PDX1 expression. Our study identifies Smndc1 as a key factor connecting splicing and chromatin remodeling to the control of insulin expression in human and mouse islet cells.
Project description:Insulin expression is restricted to the pancreatic beta cells, which are physically or functionally depleted in diabetes. Identifying targetable pathways repressing insulin in non-beta cells, particularly in the developmentally related glucagon-secreting alpha cells, is an important aim of regenerative medicine. Here, we performed an RNA interference screen in the murine alpha cell line, alphaTC1, to identify silencers of insulin expression. We discovered that knockdown of the splicing factor Smndc1 (Survival Motor Neuron Domain Containing 1) triggered a global repression of alpha cell gene-expression programs in favor of increased beta cell markers. Mechanistically, Smndc1 knockdown upregulated the key beta cell transcription factor Pdx1, by modulating the activities of the BAF and Atrx families of chromatin remodeling complexes. SMNDC1’s repressive role was conserved in human pancreatic islets, its loss triggering enhanced insulin secretion and PDX1 expression. Our study identifies Smndc1 as a key factor connecting splicing and chromatin remodeling to the control of insulin expression in human and mouse islet cells.
Project description:Insulin expression is restricted to the pancreatic beta cells, which are physically or functionally depleted in diabetes. Identifying targetable pathways repressing insulin in non-beta cells, particularly in the developmentally related glucagon-secreting alpha cells, is an important aim of regenerative medicine. Here, we performed an RNA interference screen in the murine alpha cell line, alphaTC1, to identify silencers of insulin expression. We discovered that knockdown of the splicing factor Smndc1 (Survival Motor Neuron Domain Containing 1) triggered a global repression of alpha cell gene-expression programs in favor of increased beta cell markers. Mechanistically, Smndc1 knockdown upregulated the key beta cell transcription factor Pdx1, by modulating the activities of the BAF and Atrx families of chromatin remodeling complexes. SMNDC1’s repressive role was conserved in human pancreatic islets, its loss triggering enhanced insulin secretion and PDX1 expression. Our study identifies Smndc1 as a key factor connecting splicing and chromatin remodeling to the control of insulin expression in human and mouse islet cells.