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Newman T, Ishihara T, Shaw G, Renfree MB. The structure of the TH/INS locus and the parental allele expressed are not conserved between mammals. Heredity (Edinb) 2024; 133:21-32. [PMID: 38834866 PMCID: PMC11222543 DOI: 10.1038/s41437-024-00689-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 05/01/2024] [Accepted: 05/07/2024] [Indexed: 06/06/2024] Open
Abstract
Parent-of-origin-specific expression of imprinted genes is critical for successful mammalian growth and development. Insulin, coded by the INS gene, is an important growth factor expressed from the paternal allele in the yolk sac placenta of therian mammals. The tyrosine hydroxylase gene TH encodes an enzyme involved in dopamine synthesis. TH and INS are closely associated in most vertebrates, but the mouse orthologues, Th and Ins2, are separated by repeated DNA. In mice, Th is expressed from the maternal allele, but the parental origin of expression is not known for any other mammal so it is unclear whether the maternal expression observed in the mouse represents an evolutionary divergence or an ancestral condition. We compared the length of the DNA segment between TH and INS across species and show that separation of these genes occurred in the rodent lineage with an accumulation of repeated DNA. We found that the region containing TH and INS in the tammar wallaby produces at least five distinct RNA transcripts: TH, TH-INS1, TH-INS2, lncINS and INS. Using allele-specific expression analysis, we show that the TH/INS locus is expressed from the paternal allele in pre- and postnatal tammar wallaby tissues. Determining the imprinting pattern of TH/INS in other mammals might clarify if paternal expression is the ancestral condition which has been flipped to maternal expression in rodents by the accumulation of repeat sequences.
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Affiliation(s)
- Trent Newman
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Teruhito Ishihara
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
- Epigenetics Programme, Babraham Institute, Cambridge, CB22 3AT, UK
| | - Geoff Shaw
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Marilyn B Renfree
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia.
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Nakabeppu Y. Origins of Brain Insulin and Its Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1128:1-11. [PMID: 31062322 DOI: 10.1007/978-981-13-3540-2_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The brain or central nervous system (CNS) utilizes a vast amount of energy to sustain its basic functions, and most of the energy in the brain is derived from glucose. Whole-body energy and glucose homeostasis in the periphery of the human body are regulated by insulin, while the brain had been considered as an "insulin-insensitive" organ, because bulk brain glucose uptake is not affected by insulin in either rodents and humans. However, recently it has become clear that the actions of insulin are more widespread in the CNS and are a critical part of normal development, food intake, and energy balance, as well as plasticity throughout adulthood. Moreover, there are substantial evidence demonstrating that brain insulin is derived from pancreas, neurons, and astrocytes. In this chapter, I reviewed recent progress in roles of insulin in the brain, expression of insulin genes, and multiple origins of the brain insulin.
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Affiliation(s)
- Yusaku Nakabeppu
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
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Neelankal John A, Iqbal Z, Colley S, Morahan G, Makishima M, Jiang FX. Vitamin D receptor-targeted treatment to prevent pathological dedifferentiation of pancreatic β cells under hyperglycaemic stress. DIABETES & METABOLISM 2017; 44:269-280. [PMID: 28918929 DOI: 10.1016/j.diabet.2017.07.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 06/20/2017] [Accepted: 07/14/2017] [Indexed: 12/14/2022]
Abstract
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.
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Affiliation(s)
- A Neelankal John
- Harry-Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Verdun St, Perth, 6009 Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia
| | - Z Iqbal
- Department of Chemistry, Quaid-I-Azam University Islamabad, Pakistan
| | - S Colley
- Harry-Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Verdun St, Perth, 6009 Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia
| | - G Morahan
- Harry-Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Verdun St, Perth, 6009 Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia
| | - M Makishima
- Division of Biochemistry, Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Science, 2-5-1 Shikata-cho, Kita-ku, Okayama, Japan
| | - F-X Jiang
- Harry-Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Verdun St, Perth, 6009 Western Australia, Australia; School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia.
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Templeman NM, Clee SM, Johnson JD. Suppression of hyperinsulinaemia in growing female mice provides long-term protection against obesity. Diabetologia 2015; 58:2392-402. [PMID: 26155745 PMCID: PMC4572061 DOI: 10.1007/s00125-015-3676-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 06/05/2015] [Indexed: 01/13/2023]
Abstract
AIMS/HYPOTHESIS Hyperinsulinaemia is associated with obesity but its causal role in the onset of obesity remains controversial. In this study, we tested the hypothesis that transient attenuation of diet-induced insulin hypersecretion in young mice can provide sustained protection against obesity throughout adult life. METHODS Using 'genetically humanised' mice lacking both alleles of rodent-specific Ins1, we compared mice heterozygous for the ancestral insulin gene Ins2 with Ins2(+/+) controls. Female Ins1(-/-):Ins2(+/-) and Ins1(-/-):Ins2(+/+) littermates were fed chow or high-fat diet (HFD). Insulin secretion, metabolic health variables and body mass/composition were tracked for over 1 year. We examined islet function and adipose transcript levels of adipogenic, lipogenic and lipolytic genes at two time points. RESULTS In control Ins1(-/-):Ins2(+/+) mice, HFD resulted in elevated fasting and glucose-stimulated insulin secretion between 8 weeks and 27 weeks of age. Hyperinsulinaemia was reduced by nearly 50% in Ins1(-/-):Ins2(+/-) mice during this period, without lasting adverse effects on glucose homeostasis. This corresponded with attenuated weight gain and adiposity. White adipose tissue from Ins1(-/-):Ins2(+/-) mice had fewer large lipid droplets, although transcriptional changes were not detected. Importantly, Ins1(-/-):Ins2(+/-) mice remained lighter than Ins1(-/-):Ins2(+/+) littermates despite reaching an equivalent degree of hyperinsulinaemia on HFD by 52 weeks. CONCLUSIONS/INTERPRETATION These data demonstrate that attenuation of hyperinsulinaemia in young, growing female mice provides a long-lasting protection against obesity. This protection persists despite a late-onset emergence of hyperinsulinaemia in HFD-fed Ins1(-/-):Ins2(+/-) mice. Given the evolutionary conserved roles of insulin, it is possible that suppressing hyperinsulinaemia early in life may have far-reaching consequences on obesity in full-grown adult humans.
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Affiliation(s)
- Nicole M Templeman
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3
| | - Susanne M Clee
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3
| | - James D Johnson
- Diabetes Research Group, Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3.
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Tunster SJ, Jensen AB, John RM. Imprinted genes in mouse placental development and the regulation of fetal energy stores. Reproduction 2013; 145:R117-37. [PMID: 23445556 DOI: 10.1530/rep-12-0511] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Imprinted genes, which are preferentially expressed from one or other parental chromosome as a consequence of epigenetic events in the germline, are known to functionally converge on biological processes that enable in utero development in mammals. Over 100 imprinted genes have been identified in the mouse, the majority of which are both expressed and imprinted in the placenta. The purpose of this review is to provide a summary of the current knowledge regarding imprinted gene function in the mouse placenta. Few imprinted genes have been assessed with respect to their dosage-related action in the placenta. Nonetheless, current data indicate that imprinted genes converge on two key functions of the placenta, nutrient transport and placental signalling. Murine studies may provide a greater understanding of certain human pathologies, including low birth weight and the programming of metabolic diseases in the adult, and complications of pregnancy, such as pre-eclampsia and gestational diabetes, resulting from fetuses carrying abnormal imprints.
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Affiliation(s)
- S J Tunster
- Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales CF10 3AX, UK
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A survey of tissue-specific genomic imprinting in mammals. Mol Genet Genomics 2012; 287:621-30. [PMID: 22821278 DOI: 10.1007/s00438-012-0708-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 07/03/2012] [Indexed: 01/20/2023]
Abstract
In mammals, most somatic cells contain two copies of each autosomal gene, one inherited from each parent. When a gene is expressed, both parental alleles are usually transcribed. However, a subset of genes is subject to the epigenetic silencing of one of the parental copies by genomic imprinting. In this review, we explore the evidence for variability in genomic imprinting between different tissue and cell types. We also consider why the imprinting of particular genes may be restricted to, or lost in, specific tissues and discuss the potential for high-throughput sequencing technologies in facilitating the characterisation of tissue-specific imprinting and assaying the potentially functional variations in epigenetic marks.
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Differential differences in methylation status of putative imprinted genes among cloned swine genomes. PLoS One 2012; 7:e32812. [PMID: 22393450 PMCID: PMC3290620 DOI: 10.1371/journal.pone.0032812] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 02/06/2012] [Indexed: 11/30/2022] Open
Abstract
DNA methylation is a major epigenetic modification in the mammalian genome that regulates crucial aspects of gene function. Mammalian cloning by somatic cell nuclear transfer (SCNT) often results in gestational or neonatal failure with only a small proportion of manipulated embryos producing live births. Many of the embryos that survive to term later succumb to a variety of abnormalities that are likely due to inappropriate epigenetic reprogramming. Aberrant methylation patterns of imprinted genes in cloned cattle and mice have been elucidated, but few reports have analyzed the cloned pig genome. Four surviving cloned sows that were created by ear fibroblast nuclear transfer, each with a different life span and multiple organ defects, such as heart defects and bone growth delay, were used as epigenetic study materials. First, we identified four putative differential methylation regions (DMR) of imprinted genes in the wild-type pig genome, including two maternally imprinted loci (INS and IGF2) and two paternally imprinted loci (H19 and IGF2R). Aberrant DNA methylation, either hypermethylation or hypomethylation, commonly appeared in H19 (45% of imprinted loci hypermethylated vs. 30% hypomethylated), IGF2 (40% vs. 0%), INS (50% vs. 5%), and IGF2R (15% vs. 45%) in multiple tissues from these four cloned sows compared with wild-type pigs. Our data suggest that aberrant epigenetic modifications occur frequently in the genome of cloned swine. Even with successful production of cloned swine that avoid prenatal or postnatal death, the perturbation of methylation in imprinted genes still exists, which may be one of reason for their adult pathologies and short life. Understanding the aberrant pattern of gene imprinting would permit improvements in future cloning techniques.
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Meur G, Qian Q, da Silva Xavier G, Pullen TJ, Tsuboi T, McKinnon C, Fletcher L, Tavaré JM, Hughes S, Johnson P, Rutter GA. Nucleo-cytosolic shuttling of FoxO1 directly regulates mouse Ins2 but not Ins1 gene expression in pancreatic beta cells (MIN6). J Biol Chem 2011; 286:13647-56. [PMID: 21335550 PMCID: PMC3075709 DOI: 10.1074/jbc.m110.204248] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 02/14/2011] [Indexed: 01/26/2023] Open
Abstract
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.
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Affiliation(s)
- Gargi Meur
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Qingwen Qian
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Gabriela da Silva Xavier
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Timothy J. Pullen
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
| | - Takashi Tsuboi
- the Department of Life Sciences, University of Tokyo, Tokyo 153-8902, Japan
| | - Caroline McKinnon
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Laura Fletcher
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M. Tavaré
- the Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Stephen Hughes
- the Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, and
| | - Paul Johnson
- the Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, and
| | - Guy A. Rutter
- From the Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
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Kadam S, Muthyala S, Nair P, Bhonde R. Human placenta-derived mesenchymal stem cells and islet-like cell clusters generated from these cells as a novel source for stem cell therapy in diabetes. Rev Diabet Stud 2010; 7:168-82. [PMID: 21060975 DOI: 10.1900/rds.2010.7.168] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Placental tissue holds great promise as a source of cells for regenerative medicine due to its plasticity, and easy availability. Human placenta-derived mesenchymal stem cells (hPDMSCs) have the potential to differentiate into insulin-producing cells. Upon transplantation, they can reverse experimental diabetes in mice. However, it is not known whether culture-expanded undifferentiated hPDMSCs are capable of restoring normoglycemia upon transplantation in streptozotocin (STZ)-induced diabetic mice. Hence we prepared long-term cultures of hPDMSCs from the chorionic villi of full-term human placenta. Flow cytometry analyses and immunocytochemistry study revealed bonafide mesenchymal nature of the isolated hPDMSCs. These cultures could differentiate into adipogenic, oesteogenic, chondrogenic, and neuronal lineages on exposure to lineage-specific cocktails. Furthermore, we showed that hPDMSCs can form islet-like cell clusters (ILCs) on stepwise exposure to serum-free defined media containing specific growth factors and differentiating agents. qRT-PCR showed the expression of insulin, glucagon, and somatostatin in undifferentiated hPDMSCs and in ILCs. Differentiated ILCs were found to express human insulin, glucagon, and somatostatin by immunocytochemistry. Additionally, ILCs also showed abundance of pancreatic transcription factors ngn3 and isl1. Both undifferentiated hPDMSCs and ILCs exihibited insulin secretion in response to glucose. Transplantation of hPDMSCs or ILCs derived from hPDMSCs in STZ-induced diabetic mice led to restoration of normoglycemia. Our results demonstrate, for the first time, reversal of hyperglycemia by undifferentiated hPDMSCs and ILCs derived from hPDMSCs. These results suggest human placenta-derived MSCs as an alternative source for cell replacement therapy in diabetes.
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Affiliation(s)
- Sachin Kadam
- National Center for Cell Science, Ganeshkhind, Pune 411007, MS, India
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Freyer C, Renfree MB. The mammalian yolk sac placenta. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2009; 312:545-54. [DOI: 10.1002/jez.b.21239] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Miri K, Varmuza S. Chapter 5 Imprinting and Extraembryonic Tissues—Mom Takes Control. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 276:215-62. [DOI: 10.1016/s1937-6448(09)76005-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Ager E, Suzuki S, Pask A, Shaw G, Ishino F, Renfree MB. Insulin is imprinted in the placenta of the marsupial, Macropus eugenii. Dev Biol 2007; 309:317-28. [PMID: 17706631 DOI: 10.1016/j.ydbio.2007.07.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 07/19/2007] [Accepted: 07/20/2007] [Indexed: 11/16/2022]
Abstract
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.
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Affiliation(s)
- Eleanor Ager
- Department of Zoology, The University of Melbourne, Melbourne, Victoria, 3010, Australia
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Gimelbrant AA, Chess A. An epigenetic state associated with areas of gene duplication. Genes Dev 2006; 16:723-9. [PMID: 16687731 PMCID: PMC1473183 DOI: 10.1101/gr.5023706] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 04/06/2006] [Indexed: 11/24/2022]
Abstract
Asynchronous DNA replication is an epigenetically determined feature found in all cases of monoallelic expression, including genomic imprinting, X-inactivation, and random monoallelic expression of autosomal genes such as immunoglobulins and olfactory receptor genes. Most genes of the latter class were identified in experiments focused on genes functioning in the chemosensory and immune systems. We performed an unbiased survey of asynchronous replication in the mouse genome, excluding known asynchronously replicated genes. Fully 10% (eight of 80) of the genes tested exhibited asynchronous replication. A common feature of the newly identified asynchronously replicated areas is their proximity to areas of tandem gene duplication. Testing of other clustered areas supported the idea that such regions are enriched with asynchronously replicated genes.
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Affiliation(s)
- Alexander A. Gimelbrant
- Center for Human Genetic Research, Massachusetts General Hospital and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Andrew Chess
- Center for Human Genetic Research, Massachusetts General Hospital and Department of Medicine, Harvard Medical School, Boston, Massachusetts 02114, USA
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