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:BCAS2 (Breast cancer amplified sequence 2) is involved in multiple biological processes, including pre-mRNA splicing. However, the physiological roles of BCAS2 are still largely unclear. Here we report that BCAS2 is specifically enriched in spermatogonia of mouse testes. Conditional disruption of Bcas2 in male germ cells impairs spermatogenesis and leads to male mouse infertility. Although the spermatogonia appear grossly normal, spermatocytes in meiosis prophase I and meiosis events (recombination and synapsis) are rarely observed in the BCAS2-depleted testis. In BCAS2 null testis, 245 genes are altered in alternative splicing forms; at least three spermatogenesis-related genes (Dazl, Ehmt2 and Hmga1) can be verified. In addition, disruption of Bcas2 results in a significant decrease of the full-length form and an increase of the short form (lacking exon 8) of DAZL protein. Altogether, our results suggest that BCAS2 regulates alternative splicing in spermatogonia and the transition to meiosis initiation, and male fertility.
Project description:Oocyte meiosis is an important factor affecting female reproduction. Breast cancer amplified sequence 2 (BCAS2) is a component of the spliceosome. Previous reports have shown that BCAS2 is critical in male germ cell meiosis, oocyte development, and early embryo genome integrity. However, the role of BCAS2 in oocyte meiosis has not been reported. We used Stra8-GFP-Cre mice to knock out BCAS2 during the pachytene phase of oocytes. The results of fertility tests showed that the cko mice were infertile. Morphological analysis showed that the number of primary follicles of 2M ovary was significantly reduced and follicle development was blocked. Further analysis showed that the number of primordial follicles decreased and follicle development slowed from 7dpp ovaries. Sequencing revealed that DNA damage in oocytes could not be repaired from 5dpp. There was an abnormality in meiosis, some oocytes could not reach the diplotene stage of meiosis, and more oocytes could not develop to the dictyate stage. AS analysis reveals that abnormal variable splicing of Dazl and Diaph2 Oogens-related genes in cKO mice, with involvement of the PRP19/CDC5l complex.
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: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:After the discovery of insulin a century ago, extensive work has been done to unravel the molecular network regulating insulin secretion. Here, we performed a chemical screen and identified AZD7762, a compound that potentiates glucose-stimulated insulin secretion (GSIS) of human β cell line, healthy and type 2 diabetic (T2D) human islets, and primary cynomolgus macaque islets. In vivo studies in diabetic mouse models and cynomolgus macaques demonstrated that AZD7762 enhances GSIS and improves glucose tolerance. Furthermore, genetic manipulation confirmed that ablation of CHEK2 in human β cells results in increased insulin secretion. Consistently, high-fat-diet fed Chk2-/- mice show elevated insulin secretion and improved glucose clearance. Finally, an untargeted metabolic profiling demonstrated the key role of the CHEK2-PP2A-PLK1-G6PD-PPP pathway in insulin secretion. This study successfully identifies a previously unknown insulin secretion regulating pathway that is conserved across rodents, cynomolgus macaques and human β cells in both healthy and T2D conditions.
Project description:Pancreatic beta-cells are specialized for coupling glucose metabolism to insulin peptide production and secretion. Acute glucose exposure robustly and coordinately increases translation of proinsulin and proteins required for secretion of mature insulin peptide. By contrast, chronically elevated glucose levels that occur during diabetes impair beta-cell insulin secretion and have been shown experimentally to suppress insulin translation. Whether translation of other genes critical for insulin secretion are similarly downregulated by chronic high glucose is unknown. Here, we used high-throughput ribosome profiling and nascent proteomics in MIN6 insulinoma cells to elucidate the genome-wide impact of sustained high glucose on beta-cell mRNA translation. Prior to induction of ER stress or suppression of global translation, sustained high glucose suppressed glucose-stimulated insulin secretion and downregulated translation of not only insulin, but also of mRNAs related to insulin secretory granule formation, exocytosis, and metabolism-coupled insulin secretion. Translation of these mRNAs was also downregulated in primary rat and human islets following ex-vivo incubation with sustained high glucose and in an in vivo model of chronic mild hyperglycemia. Furthermore, translational downregulation decreased cellular abundance of these proteins. Our study uncovered a translational regulatory circuit during beta-cell glucose toxicity that impairs expression of proteins with critical roles in beta-cell function.
Project description:Defective insulin secretion by pancreatic β cells underlies the development of type 2 diabetes (T2D). High fat diet-fed mice are commonly used to study diabetes progression, but studies are usually limited to a single strain, such as C57Bl/6J. Here, we use a systems biology approach to integrate large phenotypic and islet transcriptomic data sets from six commonly used strains fed a high fat or regular chow diet to identify genes associated with glucose intolerance and insulin secretion. One of these genes is Elovl2, encoding very long chain fatty acid elongase 2. ELOVL2 is responsible for the synthesis of the polyunsaturated fatty acid, docosahexaenoic acid (DHA). We show that DHA rescues glucose-induced insulin secretion and cytosolic Ca2+ influx impaired by glucolipotoxicity, and that Elovl2 over-expression is able to restore the insulin secretion defect under these conditions. We propose that increased endogenous DHA levels resulting from Elovl2 up-regulation counteracts the insulin secretion defect associated with glucolipotoxicity. Although we focus our experimental validation on Elovl2, the comprehensive data set and integrative network model we used to identify this candidate gene represents an important novel resource to dissect the molecular aetiology of β cell failure in murine models. 6 mouse strains, 4 time points, 2 diets