Pdx1- and Ngn3-Cre-mediated PLAG1 expression in the pancreas leads to endocrine hormone imbalances that affect glucose metabolism

Pleomorphic adenoma gene-like 1 (PLAGL1) has been linked to transient neonatal diabetes mellitus. Here, we investigated the role of the related pleomorphic adenoma gene 1 (PLAG1) in glucose homeostasis. PLAG1 transgenic mice in which expression of the PLAG1 transgene can be targeted to different organs by Cre-mediated modulation were crossed with Pdx1-Cre or Ngn3-Cre mice, resulting in double transgenic P1-Pdx1Cre or P1-Ngn3Cre mice, respectively. P1-Pdx1Cre and P1-Ngn3Cre mice developed hyperplasia of pancreatic islets due to increased β- and δ- but not α-cell proliferation. In young P1-Pdx1Cre mice (less than 15 weeks) there was a balanced increase in the pancreatic content of insulin and somatostatin, which was associated with normoglycemia. In older P1-Pdx1Cre mice the pancreatic somatostatin content far exceeded that of insulin, leading to the progressive development of severe hypoglycemia beyond 30 weeks. In contrast, in older P1-Ngn3Cre mice the relative increase of the pancreatic insulin content exceeded that of somatostatin and these mice remained normoglycemic. In conclusion, forced expression of PLAG1 under the control of the Pdx1 or Ngn3 promoter in murine pancreas induces different degrees of endocrine hormone imbalances within the pancreas, which is associated with hypoglycemia in P1-Pdx1Cre mice but not P1-Ngn3Cre mice. These results suggest that once stem cell-derived islet transplantations become possible, the appropriate balance between different hormone-producing cells will need to be preserved to prevent deregulated glucose metabolism.     

Improved glucose tolerance and acinar dysmorphogenesis by targeted expression of transcription factor PDX-1 to the exocrine pancreas.

The homeodomain protein PDX-1 is critical for pancreas development and is a key regulator of insulin gene expression. PDX-1 nullizygosity and haploinsufficiency in mice and humans results in pancreatic agenesis and diabetes, respectively. At embryonic day (e) 10.5, PDX-1 is expressed in all pluripotential gut-derived epithelial cells destined to differentiate into the exocrine and endocrine pancreas. At e15, PDX-1 expression is downregulated in exocrine cells, but remains high in endocrine cells. The aim of this study was to determine whether targeted overexpression of PDX-1 to the exocrine compartment of the developing pancreas at e15 would allow for respecification of the exocrine cells. Transgenic (TG) mice were generated in which PDX-1 was expressed in the exocrine pancreas using the exocrine-specific elastase-1 promoter. These mice exhibited a marked dysmorphogenesis of the exocrine pancreas, manifested by increased rates of replication and apoptosis in acinar cells and a progressive fatty infiltration of the exocrine pancreas with age. Interestingly, the TG mice exhibited improved glucose tolerance, but absolute beta-cell mass was not increased. These findings indicate that downregulation of PDX-1 is required for the proper maintenance of the exocrine cell phenotype and that upregulation of PDX-1 in acinar cells affects beta-cell function. The mechanisms underlying these observations remain to be elucidated.     

骨肉瘤中cbfa1基因表达与临床因素的相关性研究

目的 ｃｂｆａｌ基因是一种结合在Ｏｓｔｅｏｃａｌｃｉｎ启动子上并能调节其在成骨细胞中表达的转录因子,在成骨细胞的分化和成熟中起着重要的作用。由于ｃｂｆａｌ基因在成骨分化过程中所起的重要作用。研究骨肉瘤中ｃｂｆａｌ的表达有重要的意义。方法 应用Ｓｏｕｔｈｅｒｎ ｂｌｏｔ法ＲＴ－ＰＣＲ技术对４３例骨肉瘤标本和３株骨肉瘤细胞系（ＳＯＳ－２,ＨＯＳ和Ｕ－２）中ｃｂｆａｌ基因的结构和表达进行了研究。     

Development of beta-cells in the native pancreas after pancreas allo-transplantation in the Spontaneously Diabetic Torii rat

BACKGROUND: We previously demonstrated the development of beta-cells in the native pancreas after syngeneic pancreas transplantation (PTx) in a model of type 2 diabetes, namely the Spontaneously Diabetic Torii (SDT; RT1 a) rat. In this study, we evaluated the effect of fully allogeneic PTx (allo-PTx) under immunosuppression on the native pancreases in the recipients. MATERIALS AND METHODS: Diabetic 25-week-old SDT rats were divided into two groups: untreated controls and PTx-treated recipients. Dark Agouti (RT1 a) pancreases were then transplanted into the SDT rats. FK506 was administered daily postoperatively. Each group was examined for 15 weeks. RESULTS: Control SDT rats showed a disappearance of the pancreatic and duodenal homeobox-1 (PDX-1) expression of the pancreases with the development of diabetes. In addition, the islets were gradually replaced by fibrosis, thus resulting in a marked decrease in the beta-cell mass at 40 weeks of age. On the other hand, in PTx recipients, islet-like cell clusters were found in the native pancreases. The beta-cell mass significantly increased in the native pancreases in the recipients at 10 and 15 weeks posttransplantation in comparison to the age-matched controls. Moreover, we observed the re-expression of PDX-1 in the islet-like cell clusters. Interestingly, insulin and glucagon double-positive stained cells in the mesenchyme and insulin single-positive cells in the ductal epithelium were also observed. CONCLUSIONS: Our results indicated that the benefits of avoiding glucose toxicity by allo-PTx under immunosuppression could therefore induce the PDX-1 expression in the native pancreases, thus potentially resulting in the development of beta-cells in type 2 diabetic recipients.     

Hint1基因抑制HepG2细胞AP-1转录因子活性的实验研究

目的 探索体外过表达Hint1基因对人肝肿瘤HepG2细胞AP-1转录因子活性的影响.方法 分子克隆获得Hint1基因序列,构建pHA-Hint1重组融合基因表达载体.阳离子脂质体介导,pHA-Hint1转导人肝母细胞瘤HepG2细胞,RT-PCR和Western blot检测HepG2细胞中外源HA-Hint1表达.pHA-Hint1质粒、启动子荧光素酶报告质粒AP-1/Luc及巨细胞病毒-β-半乳糖酶报告质粒(β-gel)共转导HepG2细胞.36 h后测定荧光素酶活性及β-gel活性.结果 重组质粒经EcoR Ⅰ和BamH Ⅰ双酶切,获约100 bp特异条带,测序证实成功构建pHA-Hint1表达载体.pHA-Hint1及空载体pcDNA3/HA转导HepG2细胞,半定量RT-PCR结果显示pHA-Hint1组Hint1mRNA表达高于空载体组(t=3.89,P<0.05);Western blot结果显示pHA-Hint1组HA标签蛋白表达高于空载体组(t=3.12,P<0.05).AP-1转录因子活性检测结果:pHA-Hint1终浓度为0 μg/ml,0.5 μg/ml,1.0 μg/ml,1.5 μg/ml,2.0 μg/ml时,AP-1转录因子相对活性(106)为:5.12±0025、4.24±0.74、3.43±0.31、2.62±0.48、2.09±0.21.随着pHA-Hint1浓度增加,荧光素酶活性呈明显下降,当pHA-Hint1浓度达到1.5 μg及2.0 μg时,差异有统计学意义(F=72.009,P<0.05).结论 过表达Hint1基因可抑制HepG2细胞AP-1转录因子活性.