Somatostatin Inhibits Insulin-Gene Expression Through a Posttranscriptional Mechanism in a Hamster Islet Cell Line

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 244-249 ◽  
Author(s):  
J. Philippe
Keyword(s):  
Gene Expression ◽  
Cell Line ◽  
Islet Cell ◽  
Insulin Gene ◽  
Insulin Gene Expression

Differential expression of non-allelic insulin genes in rodent islet tumour cells

1993 ◽  
Vol 11 (3) ◽  
pp. 305-318 ◽  
Author(s):  
K Lund ◽  
N Blume ◽  
B K Michelsen ◽  
D Bucchini ◽  
O D Madsen
Keyword(s):  
Gene Expression ◽  
Cell Line ◽  
Islet Cell ◽  
Tumour Cells ◽  
Insulin Gene ◽  
Cell Phenotype ◽  
Β Cell ◽  
C Peptide ◽  
Insulin Gene Expression

ABSTRACT We have compared the expression patterns of the non-allelic insulin 1 and 2 genes during prolonged in-vitro culture of the mouse islet cell line β-TC3, where transformation by the SV40 T oncoprotein is targeted to the differentiated β-cell phenotype, and the rat islet cell line NHI-6F, in which the β-cell phenotype is induced by transient in-vivo passage. The NHI-6F clone carries, in addition, a single copy of a transfected silent human insulin gene which contains 3 kb of regulatory sequences known to confer β-cell-specific expression. Insulin gene expression was measured by an assay based on a reverse transcription-polymerase chain reaction, to determine whether the ancestral rodent insulin 2 genes (and the human homologue in the NHI-6F cells) are regulated differently from the duplicated rat and mouse insulin 1 genes. We have shown that activation of insulin gene expression in the NHI-6F cells includes transcriptional activation of all three genes, but that extended propagation of tumour cells in vitro leads to a selective and equal decline in the quantities of transcripts from the rat 2 and human genes relative to transcripts from the rat 1 gene. In the later passages, insulin transcripts were derived almost exclusively from the rat 1 gene. In early in-vitro passages of the mouse endocrine cell line β-TC3, the expression pattern of the mouse 1 and 2 insulin genes resembled that seen in isolated mouse islets. After more than 45 in-vitro passages, expression of the duplicated mouse 1 gene decreased tenfold when compared with the ancestral mouse 2 gene. As previously shown for NHI-6F cells, the differential expression of non-allelic insulin genes in the β-TC3 line was also clearly evident at the cellular level, where a subpopulation of cells selectively expressed readily detectable levels of mouse C-peptide 2 immunoreactivity while devoid of C-peptide 1. Our results suggest that the maintenance of insulin gene expression in rodent tumour cells is influenced by enhancer sequences which are not shared by the ancestral and duplicated insulin genes, and that either species-specific conditions or transformation-related differences exist between the rat and mouse cell lines that govern which gene remains active during prolonged in-vitro propagation.

scholarly journals Differentially expressed Maf family transcription factors, c-Maf and MafA, activate glucagon and insulin gene expression in pancreatic islet alpha- and beta-cells

2004 ◽  
Vol 32 (1) ◽  
pp. 9-20 ◽  
Author(s):  
K Kataoka ◽  
S Shioda ◽  
K Ando ◽  
K Sakagami ◽  
H Handa ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Cell Line ◽  
Beta Cells ◽  
Cell Lines ◽  
Promoter Activity ◽  
Insulin Gene ◽  
Insulinoma Cell ◽  
Insulin Gene Expression ◽  
Glucagon And Insulin

A basic-leucine zipper transcription factor, MafA, was recently identified as one of the most important transactivators of insulin gene expression. This protein controls the glucose-regulated and pancreatic beta-cell-specific expression of the insulin gene through a cis-regulatory element called RIPE3b/MARE (Maf-recognition element). Here, we show that MafA expression is restricted to beta-cells of pancreatic islets in vivo and in insulinoma cell lines. We also demonstrate that c-Maf, another member of the Maf family of transcription factors, is expressed in islet alpha-cells and in a glucagonoma cell line (alphaTC1), but not in gamma- and delta-cells. An insulinoma cell line, betaTC6, also expressed c-Maf, albeit at a low level. Chromatin immunoprecipitation assays demonstrated that Maf proteins associate with insulin and glucagon promoters in beta- and alpha-cell lines, respectively. c-Maf protein stimulated glucagon promoter activity in a transient luciferase assay, and activation of the glucagon promoter by c-Maf was more efficient than by the other alpha-cell-enriched transcription factors, Cdx2, Pax6, and Isl-1. Furthermore, inhibition of c-Maf expression in alphaTC1 cells by specific short hairpin RNA resulted in marked reduction of the glucagon promoter activity. Thus, c-Maf and MafA are differentially expressed in alpha- and beta-cells where they regulate glucagon and insulin gene expression, respectively.

scholarly journals Homologous DNA sequences and cellular factors are implicated in the control of glucagon and insulin gene expression.

1995 ◽  
Vol 15 (7) ◽  
pp. 3904-3916 ◽  
Author(s):  
M Cordier-Bussat ◽  
C Morel ◽  
J Philippe
Keyword(s):  
Gene Expression ◽  
Binding Sites ◽  
Islet Cell ◽  
Insulin Gene ◽  
Control Element ◽  
Alpha Cells ◽  
Specific Element ◽  
Proximal Site ◽  
Insulin Gene Expression ◽  
Glucagon And Insulin

The glucagon gene is specifically expressed in the alpha cells of pancreatic islets. The promoter of the glucagon gene is responsible for this specificity. Within the promoter, the upstream promoter element G1 is critical to restrict expression to the alpha cells. We define here a composite DNA control element, G4, localized upstream of G1 between nucleotides -100 and -140 which functions as an islet-specific activator in both glucagon- and insulin-producing cells but not in nonislet cells. G4 contains at least three protein binding sites. The most proximal site, E2, is highly homologous to the E1, SMS-UE, and B elements of the rat insulin I, somastatin, and elastase I genes, respectively, and interacts with a pancreas-specific complex; the distal site, E3, represents an E box which is identical to the E boxes of the rat insulin I and II genes and binds to a complex similar or identical to IEF1 which has been implicated in the tissue-specific control of insulin gene expression. These two sites necessitate a third element, the intervening sequence, to activate transcription. We conclude that the first 140 bp of the glucagon gene promoter contains at least two DNA control elements responsible for pancreatic alpha-cell-specific expression: G4, an islet cell-specific element sharing common binding sites with the insulin gene, and G1, which restricts glucagon gene expression to the alpha cells. This double control of specificity might have relevance during islet cell differentiation.

scholarly journals Role of Cdx-2 in insulin and proglucagon gene expression: a study using the RIN-1056A cell line with an inducible gene expression system

2005 ◽  
Vol 186 (1) ◽  
pp. 179-192 ◽  
Author(s):  
Yi Zhao ◽  
Tao Liu ◽  
Nina Zhang ◽  
Fenghua Yi ◽  
Qinghua Wang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Line ◽  
Cell Lines ◽  
Expression System ◽  
Insulin Gene ◽  
Luciferase Reporter ◽  
Luciferase Reporter Gene ◽  
Gene Expressions ◽  
Insulin Gene Expression

Although the homeobox gene Cdx-2 was initially isolated from the pancreatic β cell line HIT-T15, no examination of its role in regulating endogenous insulin gene expression has been reported. To explore further the role of Cdx-2 in regulating both insulin and proglucagon gene expression, we established an ecdysone-inducible Cdx-2 expression system. This report describes a study using the rat insulinoma cell line RIN-1056A, which abundantly expresses both insulin and proglucagon (glu), and relatively high amounts of endogenous Cdx-2. Following the introduction of the inducible Cdx-2 expression system into this cell line and the antibiotic selection procedure, we obtained novel cell lines that displayed dramatically reduced expression of endogenous Cdx-2, in the absence of the inducer. These novel cell lines did not express detectable amounts of glu mRNA or the glucagon hormone, while their insulin expression was not substantially affected. In the presence of the inducer, however, transfected Cdx-2 expression was dramatically increased, accompanied by stimulation of endogenous Cdx-2 expression. More importantly, activated Cdx-2 expression was accompanied by elevated insulin mRNA expression, and insulin synthesis. Cdx-2 bound to the insulin gene promoter enhancer elements, and stimulated the expression of a luciferase reporter gene driven by these enhancer elements. Furthermore, Cdx-2 and insulin gene expressions in the wild-type RIN-1056A cells were stimulated by forskolin treatment, and forskolin-mediated activation on insulin gene expression was attenuated in the absence of Cdx-2. We suggest that Cdx-2 may mediate the second messenger cAMP in regulating insulin gene transcription.

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