Differential expression and imprinting status of Ins1 and Ins2 genes in extraembryonic tissues of laboratory mice

doi:10.1016/j.modgep.2004.04.013

Gene Expression Patterns

Volume 5, Issue 2, December 2004, Pages 297-300

https://doi.org/10.1016/j.modgep.2004.04.013 Get rights and content

Abstract

There are two functional insulin genes in the mouse genome. The Ins2 gene is imprinted and expressed monoallelically from the paternal allele in the yolk sac. In the present study we have re-examined the imprinting status of Ins1. We found that Ins1 is not expressed in the yolk sac of several laboratory mouse strains. The asynchrony of replication at the wild type locus was significantly lower than at imprinted loci and was more similar to non-imprinted loci. Finally, we have taken the advantage of the Ins1^neo allele created by homologous recombination to examine the allelic usage at this locus. We observed that the neo gene inserted at the Ins1 locus was expressed from both the paternally and the maternally transmitted allele. Therefore, the Ins1 gene does not share any of the basic properties of imprinted genes. On the basis of these data, we concluded that Ins1 locus is unlikely to be imprinted in common laboratory mice.

Section snippets

Results and discussion

Mice, rat, xenopus and some fishes, have two non-allelic Insulin genes. These genes are both functional and the two proteins are synthetized in the pancreas in a 1:2 ratio for Ins1 and Ins2, respectively (Deltour et al., 1993). The Ins1 gene arose by retrotransposition of a partially processed Ins2 transcript and is highly similar to it but lacks the second intron. Ins1 maps to the telomeric region of the mouse chromosome 19 (Davies et al., 1994). The single Ins gene found in human, pork,

Experimental procedures

Yolk sacs were collected from laboratory mouse strains 129, Blsw, C57Bl6 and B6CBAF1. Mice with the Ins1 gene replaced by the pmc-neo reporter gene by targeted mutation were described earlier (Duvillié et al., 1997). Normal foetuses were obtained after mating the females to males of the same genotype. Heterozygous mutant foetuses with the mutant allele transmitted either by the father or by the mother were obtained by mating homozygous mutant animals with wild type mice (C57BlxCBA/J F1).

Acknowledgements

The authors are grateful to Lucianne Lamotte for assistance and Takuya Imamura for helpful discussions and critical reading of the manuscript.

References (12)

P. Davies et al.
Genetic re-assignment of the insulin-1 (Ins1) gene to distal mouse chromosome 19
Genomics
(1994)
L. Deltour et al.
Tissue- and developmental stage-specific imprinting of the mouse proinsulin gene, Ins2
Dev. Biol.
(1995)
B. Duvillié et al.
Imprinting at the mouse Ins2 locus: evidence for cis- and trans-allelic interactions
Genomics
(1998)
A. Pàldi
Genomic imprinting: could the chromatin structure be the driving force?
Curr. Top. Dev. Biol.
(2003)
L. Deltour et al.
Discrimination of homologous mRNAs by polymerase chain reaction
Methods Mol. Cell. Biol.
(1992)
L. Deltour et al.
Differential expression of the two nonallelic proinsulin genes in the developing mouse embryo
Proc. Natl. Acad. Sci. USA
(1993)

There are more references available in the full text version of this article.

Cited by (14)

Insulin biosynthesis and release in health and disease
2024, Insulin: Deficiency, Excess and Resistance in Human Disease
The discovery of insulin changed the landscape of diabetes treatment and research. The name insulin(e)—which came from the Latin word “insula” with reference to a hypothetical molecule that was secreted by the Islets of Langerhans—was coined by Jean de Meyer and Edward Albert Sharpey-Schafer, before the isolation of the peptide hormone by Banting and Best. Since its discovery, much effort has been expanded in understanding the synthesis and release of insulin in health and disease in order to allow us to understand better its role in the regulation of blood glucose concentrations and through this understanding, to allow us to develop better treatment for diabetes. In this chapter, we will review published data on the regulation of insulin biosynthesis and release in rodent and human pancreatic β-cells and discuss how the concerted regulation of these processes contributes to systemic glucose homeostasis.
Vitamin D receptor-targeted treatment to prevent pathological dedifferentiation of pancreatic β cells under hyperglycaemic stress
2018, Diabetes and Metabolism
Citation Excerpt :
Insulin exocytosis from insulin granules is indicated by alterations in the ATP-to-ADP ratio within β cells. Synthesis of insulin in mouse islets derives from both insulin 1 (Ins1) and insulin 2 (Ins2) genes under the control of two major transcription factors: v-maf avian musculoaponeurotic fibrosarcoma oncogene homologue F (MafA) and pancreas/duodenum homeobox protein 1 (Pdx1) [22]. These have direct control over the expression of insulin genes by binding to promoters of these genes.
Dedifferentiation has been identified as one of the causes of β-cell failure resulting in type 2 diabetes (T2D). This study tested whether increasing vitamin D receptor (VDR) expression prevents dedifferentiation of β cells in a high-glucose state in vitro. Culturing a mouse insulinoma cell line (MIN6) in a high-glucose environment decreased VDR expression. However, increased VDR following vitamin D3 (VD3) treatment improved insulin release of early-passage MIN6 and insulin index of db/- (heterozygous) islets to levels seen in normal functional islets. Treatment with VD3, its analogues and derivatives also increased the expression of essential transcription factors, such as Pdx1, MafA and VDR itself, ultimately increasing expression of Ins1 and Ins2, which might protect β cells against dedifferentiation. VD3 agonist lithocholic acid (LCA) propionate was the most potent candidate molecule for protecting against dedifferentiation, and an e-pharmacophore mapping model confirmed that LCA propionate exhibits a stabilizing conformation within the VDR binding site. This study concluded that treating db/+ islets with a VD3 analogue and/or derivatives can increase VDR activity, preventing the pathological dedifferentiation of β cells and the onset of T2D.
Nucleo-cytosolic shuttling of FoxO1 directly regulates mouse Ins2 but not Ins1 gene expression in pancreatic beta cells (MIN6
2011, Journal of Biological Chemistry
Citation Excerpt :
None of these regions was present in mouse or rat Ins1 genes. It is important to emphasize that the origin and regulation of the Ins2 and Ins1 genes in rodents differs: the Ins1 gene seems likely to be a functional retroposon of Ins2 emerging later in evolution (49), and unlike Ins2 the former lacks genetic imprinting and expresses from both alleles (50). “Snapshot” measurements of the precise number of Ins1 and Ins2 mRNA molecules expressed in single primary β cells from mouse islets incubated at low (5 mm) and high (20 mm) glucose concentrations also indicated differential expression and inducibility of the two insulin genes previously, Ins2 mRNA being 3-fold and 2-fold higher than Ins1 mRNA at low and high glucose, respectively (51).
The Forkhead box transcription factor FoxO1 regulates metabolic gene expression in mammals. FoxO1 activity is tightly controlled by phosphatidylinositol 3-kinase (PI3K) signaling, resulting in its phosphorylation and nuclear exclusion. We sought here to determine the mechanisms involved in glucose and insulin-stimulated nuclear shuttling of FoxO1 in pancreatic β cells and its consequences for preproinsulin (Ins1, Ins2) gene expression. Nuclear-localized endogenous FoxO1 translocated to the cytosol in response to elevated glucose (3 versus 16.7 mm) in human islet β cells. Real-time confocal imaging of nucleo-cytosolic shuttling of a FoxO1-EGFP chimera in primary mouse and clonal MIN6 β cells revealed a time-dependent glucose-responsive nuclear export, also mimicked by exogenous insulin, and blocked by suppressing insulin secretion. Constitutively active PI3K or protein kinase B/Akt exerted similar effects, while inhibitors of PI3K, but not of glycogen synthase kinase-3 or p70 S6 kinase, blocked nuclear export. FoxO1 overexpression reversed the activation by glucose of pancreatic duodenum homeobox-1 (Pdx1) transcription. Silencing of FoxO1 significantly elevated the expression of mouse Ins2, but not Ins1, mRNA at 3 mm glucose. Putative FoxO1 binding sites were identified in the distal promoter of rodent Ins2 genes and direct binding of FoxO1 to the Ins2 promoter was demonstrated by chromatin immunoprecipitation. A 915-bp glucose-responsive Ins2 promoter was inhibited by constitutively active FoxO1, an effect unaltered by simultaneous overexpression of PDX1. We conclude that nuclear import of FoxO1 contributes to the suppression of Pdx1 and Ins2 gene expression at low glucose, the latter via a previously unsuspected and direct physical interaction with the Ins2 promoter.
Chapter 5 Imprinting and Extraembryonic Tissues-Mom Takes Control
2009, International Review of Cell and Molecular Biology
Genomic imprinting is an epigenetic mechanism that silences one parental allele of a small subset of genes. Many imprinted genes exhibit this property only in extraembryonic tissues—placenta and yolk sac. This has led to the idea that imprinting in mammals coevolved with some aspect of placentation. Nevertheless, many studies of imprinting have ignored the extraembryonic tissues, the yolk sac and its precursor, the primitive endoderm, in particular. The primitive endoderm is involved in very early signaling events during a critical stage in development, gastrulation, during which body plan axes and head process neuroectoderm are established. Improper signaling from primitive endoderm as a result of abnormal expression of imprinted genes has the capacity to effect long‐term defects in embryonic/fetal tissues that might hitherto have been overlooked. We discuss these gaps in the knowledge, propose a mechanism for genomic imprinting based on current data, and suggest a line of investigation that will expand our understanding of this unique regulatory mechanism and its impact on development.
Insulin is imprinted in the placenta of the marsupial, Macropus eugenii
2007, Developmental Biology
Citation Excerpt :
The residual expression from the maternal allele, however, suggests incomplete imprinting of INS occurs in the tammar, as in other imprinted genes in marsupials (Suzuki et al., 2005). In the mouse, expression of Ins2 expression is initially biallelic and becomes monoallelic towards the end of gestation and then remains monoallelic (Deltour et al., 1995, 2004). In the tammar, the magnitude of allelic bias in INS expression varied between individual animals, with the dominant allele accounting for between 64.5% and 83% of INS expression.
Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals have a yolk sac, but while both chorio-allantoic and chorio-vitelline (yolk sac) placentation can occur, most marsupials only develop a yolk sac placenta. Insulin (INS) is unusual in that it is the only gene that is imprinted exclusively in the yolk sac placenta. Marsupials, therefore, provide a unique opportunity to examine the conservation of INS imprinting in mammalian yolk sac placentation. Marsupial INS was cloned and its imprint status in the yolk sac placenta of the tammar wallaby, Macropus eugenii, examined. In two informative individuals of the eight that showed imprinting, INS was paternally expressed. INS protein was restricted to the yolk sac endoderm, while insulin receptor, IR, protein was additionally expressed in the trophoblast. INS protein increased during late gestation up to 2 days before birth, but was low the day before and on the day of birth. The conservation of imprinted expression of insulin in the yolk sac placenta of divergent mammalian species suggests that it is of critical importance in the yolk sac placenta. The restriction of imprinting to the yolk sac suggests that imprinting of INS evolved in the chorio-vitelline placenta independently of other tissues in the therian ancestor of marsupials and eutherians.
Origins of brain insulin and its function
2019, Advances in Experimental Medicine and Biology

View all citing articles on Scopus

¹: Present address: Sangamo Biosciences Inc., 501 Canal Blvd, suite A100, Richmond, CA 94804, USA.

View full text

Article preview

Gene Expression Patterns

Abstract

Section snippets

Results and discussion

Experimental procedures

Acknowledgements

References (12)

Genetic re-assignment of the insulin-1 (Ins1) gene to distal mouse chromosome 19

Genomics

Tissue- and developmental stage-specific imprinting of the mouse proinsulin gene, Ins2

Dev. Biol.

Imprinting at the mouse Ins2 locus: evidence for cis- and trans-allelic interactions

Genomics

Genomic imprinting: could the chromatin structure be the driving force?

Curr. Top. Dev. Biol.

Discrimination of homologous mRNAs by polymerase chain reaction

Methods Mol. Cell. Biol.

Differential expression of the two nonallelic proinsulin genes in the developing mouse embryo

Proc. Natl. Acad. Sci. USA

Cited by (14)

Insulin biosynthesis and release in health and disease

Vitamin D receptor-targeted treatment to prevent pathological dedifferentiation of pancreatic β cells under hyperglycaemic stress

Nucleo-cytosolic shuttling of FoxO1 directly regulates mouse Ins2 but not Ins1 gene expression in pancreatic beta cells (MIN6

Chapter 5 Imprinting and Extraembryonic Tissues-Mom Takes Control

Insulin is imprinted in the placenta of the marsupial, Macropus eugenii

Origins of brain insulin and its function