RESUMEN
The genetic mechanisms that determine the size of the adult pancreas are poorly understood. Imprinted genes, which are expressed in a parent-of-origin-specific manner, are known to have important roles in development, growth and metabolism. However, our knowledge regarding their roles in the control of pancreatic growth and function remains limited. Here we show that many imprinted genes are highly expressed in pancreatic mesenchyme-derived cells and explore the role of the paternally-expressed insulin-like growth factor 2 (Igf2) gene in mesenchymal and epithelial pancreatic lineages using a newly developed conditional Igf2 mouse model. Mesenchyme-specific Igf2 deletion results in acinar and beta-cell hypoplasia, postnatal whole-body growth restriction and maternal glucose intolerance during pregnancy, suggesting that the mesenchyme is a developmental reservoir of IGF2 used for paracrine signalling. The unique actions of mesenchymal IGF2 are demonstrated by the absence of any discernible growth or functional phenotypes upon Igf2 deletion in the developing pancreatic epithelium. Additionally, increased IGF2 levels specifically in the mesenchyme, through conditional Igf2 loss-of-imprinting or Igf2r deletion, leads to pancreatic acinar overgrowth. Furthermore, ex-vivo exposure of primary acinar cells to exogenous IGF2 activates AKT, a key signalling node, and increases their number and amylase production. Based on these findings, we propose that mesenchymal Igf2, and perhaps other imprinted genes, are key developmental regulators of adult pancreas size and function.
Asunto(s)
Factor II del Crecimiento Similar a la Insulina/genética , Mesodermo/crecimiento & desarrollo , Páncreas/crecimiento & desarrollo , Comunicación Paracrina/genética , Células Acinares/metabolismo , Células Acinares/patología , Aminoácidos/genética , Animales , Linaje de la Célula/genética , Cromo , Metilación de ADN/genética , Femenino , Citometría de Flujo , Regulación del Desarrollo de la Expresión Génica/genética , Impresión Genómica/genética , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patología , Ratones , Ácidos Nicotínicos/genética , Páncreas/citología , Páncreas/metabolismo , Embarazo , ARN Largo no Codificante/genéticaRESUMEN
Antenatal stress increases the prevalence of diseases in later life, which shows a strong sex-specific effect. However, the underlying mechanisms remain unknown. Maternal glucocorticoids can be elevated by stress and are potential candidates to mediate the effects of stress on the offspring sex-specifically. A comprehensive evaluation of dynamic maternal and placental mechanisms modulating fetal glucocorticoid exposure upon maternal stress was long overdue. Here, we addressed this gap in knowledge by investigating sex-specific responses to midgestational stress in mice. We observed increased levels of maternal corticosterone, the main glucocorticoid in rodents, along with higher corticosteroid-binding globulin levels at midgestation in C57Bl/6 dams exposed to sound stress. This resulted in elevated corticosterone in female fetuses, whereas male offspring were unaffected. We identified that increased placental expression of the glucocorticoid-inactivating enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2; Hsd11b2 gene) and ATP-binding cassette transporters, which mediate glucocorticoid efflux toward maternal circulation, protect male offspring from maternal glucocorticoid surges. We generated mice with an Hsd11b2 placental-specific disruption (Hsd11b2PKO) and observed moderately elevated corticosterone levels in offspring, along with increased body weight. Subsequently, we assessed downstream glucocorticoid receptors and observed a sex-specific differential modulation of placental Tsc22d3 expression, which encodes the glucocorticoid-induced leucine zipper protein in response to stress. Taken together, our observations highlight the existence of unique and well-orchestrated mechanisms that control glucocorticoid transfer, exposure, and metabolism in the mouse placenta, pinpointing toward the existence of sex-specific fetal glucocorticoid exposure windows during gestation in mice.
Asunto(s)
Feto/metabolismo , Glucocorticoides/metabolismo , Placenta/metabolismo , Caracteres Sexuales , Estrés Psicológico/metabolismo , 11-beta-Hidroxiesteroide Deshidrogenasa de Tipo 2/genética , Animales , Aromatasa/genética , Corticosterona/metabolismo , Femenino , Masculino , Ratones , Ratones Endogámicos C57BL , Embarazo , Complicaciones del Embarazo/metabolismo , Complicaciones del Embarazo/psicología , Receptores de Glucocorticoides/metabolismo , Estrés Psicológico/genéticaRESUMEN
The placenta is the main determinant of fetal growth and development in utero. It supplies all the nutrients and oxygen required for fetal growth and secretes hormones that facilitate maternal allocation of nutrients to the fetus. Furthermore, the placenta responds to nutritional and metabolic signals in the mother by altering its structural and functional phenotype, which can lead to changes in maternal resource allocation to the fetus. The molecular mechanisms by which the placenta senses and responds to environmental cues are poorly understood. This review discusses the role of the insulin-like growth factors (IGFs) in controlling placental resource allocation to fetal growth, particularly in response to adverse gestational environments. In particular, it assesses the impact of the IGFs and their signalling machinery on placental morphogenesis, substrate transport and hormone secretion, primarily in the laboratory species, although it draws on data from human and other species where relevant. It also considers the role of the IGFs as environmental signals in linking resource availability to fetal growth through changes in the morphological and functional phenotype of the placenta. As altered fetal growth is associated with increased perinatal morbidity and mortality and a greater risk of developing adult-onset diseases in later life, understanding the role of IGFs during pregnancy in regulating placental resource allocation to fetal growth is important for identifying the mechanisms underlying the developmental programming of offspring phenotype by suboptimal intrauterine growth.
Asunto(s)
Desarrollo Fetal/fisiología , Placenta/fisiología , Somatomedinas/fisiología , Animales , Femenino , Humanos , Fenotipo , EmbarazoRESUMEN
AIMS/HYPOTHESIS: Ageing is a major risk factor for development of metabolic diseases such as type 2 diabetes. Identification of the mechanisms underlying this association could help to elucidate the relationship between age-associated progressive loss of metabolic health and development of type 2 diabetes. We aimed to determine molecular signatures during ageing in the endocrine pancreas. METHODS: Global gene transcription was measured in pancreatic islets isolated from young and old rats by Ilumina BeadChip arrays. Promoter DNA methylation was measured by Sequenom MassArray in 46 genes that showed differential expression with age, and correlations with expression were established. Alterations in morphological and cellular processes with age were determined by immunohistochemical methods. RESULTS: Age-related changes in gene expression were found at 623 loci (>1.5-fold, false discovery rate [FDR] <5%), with a significant (FDR < 0.05) enrichment in genes previously implicated in islet-cell function (Enpp1, Abcc8), type 2 diabetes (Tspan8, Kcnq1), inflammatory processes (Cxcl9, Il33) and extracellular matrix organisation (Col3a1, Dpt). Age-associated transcriptional differences negatively correlated with promoter DNA methylation at several loci related to inflammation, glucose homeostasis, cell proliferation and cell-matrix interactions (Il33, Cxcl9, Gpr119, Fbp2, Col3a1, Dpt, Spp1). CONCLUSIONS/INTERPRETATION: Our findings suggest that a significant proportion of pancreatic islets develop a low-grade 'chronic' inflammatory status with ageing and this may trigger altered functional plasticity. Furthermore, we identified changes in expression of genes previously linked to type 2 diabetes and associated changes in DNA methylation that could explain their age-associated dysregulation. These findings provide new insights into key (epi)genetic signatures of the ageing process in islets.
Asunto(s)
Envejecimiento/fisiología , Diabetes Mellitus Tipo 2/etiología , Inflamación/genética , Islotes Pancreáticos/metabolismo , Envejecimiento/genética , Animales , Quimiocina CXCL9/genética , Colágeno Tipo III/genética , Metilación de ADN/genética , Diabetes Mellitus Tipo 2/metabolismo , Epigénesis Genética/genética , Inflamación/metabolismo , Canal de Potasio KCNQ1/genética , Masculino , Hidrolasas Diéster Fosfóricas/genética , Pirofosfatasas/genética , Ratas , Receptores de Sulfonilureas/genética , Tetraspaninas/genéticaRESUMEN
The development of the endocrine pancreas is controlled by a hierarchical network of transcriptional regulators. It is increasingly evident that this requires a tightly interconnected epigenetic "programme" to drive endocrine cell differentiation and maintain islet function. Epigenetic regulators such as DNA and histone-modifying enzymes are now known to contribute to determination of pancreatic cell lineage, maintenance of cellular differentiation states, and normal functioning of adult pancreatic endocrine cells. Persistent effects of an early suboptimal environment, known to increase risk of type 2 diabetes in later life, can alter the epigenetic control of transcriptional master regulators, such as Hnf4a and Pdx1. Recent genome-wide analyses also suggest that an altered epigenetic landscape is associated with the ß cell failure observed in type 2 diabetes and aging. At the cellular level, epigenetic mechanisms may provide a mechanistic link between energy metabolism and stable patterns of gene expression. Key energy metabolites influence the activity of epigenetic regulators, which in turn alter transcription to maintain cellular homeostasis. The challenge is now to understand the detailed molecular mechanisms that underlie these diverse roles of epigenetics, and the extent to which they contribute to the pathogenesis of type 2 diabetes. In-depth understanding of the developmental and environmental epigenetic programming of the endocrine pancreas has the potential to lead to novel therapeutic approaches in diabetes.
Asunto(s)
Diabetes Mellitus Tipo 2/genética , Epigénesis Genética , Islotes Pancreáticos/crecimiento & desarrollo , Islotes Pancreáticos/metabolismo , Animales , Diabetes Mellitus Tipo 2/patología , Regulación del Desarrollo de la Expresión Génica , Interacción Gen-Ambiente , Humanos , Islotes Pancreáticos/patologíaRESUMEN
Environmental factors interact with the genome throughout life to determine gene expression and, consequently, tissue function and disease risk. One such factor that is known to play an important role in determining long-term metabolic health is diet during critical periods of development. Epigenetic regulation of gene expression has been implicated in mediating these programming effects of early diet. The precise epigenetic mechanisms that underlie these effects remain largely unknown. Here, we show that the transcription factor Hnf4a, which has been implicated in the etiology of type 2 diabetes (T2D), is epigenetically regulated by maternal diet and aging in rat islets. Transcriptional activity of Hnf4a in islets is restricted to the distal P2 promoter through its open chromatin configuration and an islet-specific interaction between the P2 promoter and a downstream enhancer. Exposure to suboptimal nutrition during early development leads to epigenetic silencing at the enhancer region, which weakens the P2 promoter-enhancer interaction and results in a permanent reduction in Hnf4a expression. Aging leads to progressive epigenetic silencing of the entire Hnf4a locus in islets, an effect that is more pronounced in rats exposed to a poor maternal diet. Our findings provide evidence for environmentally induced epigenetic changes at the Hnf4a enhancer that alter its interaction with the P2 promoter, and consequently determine T2D risk. We therefore propose that environmentally induced changes in promoter-enhancer interactions represent a fundamental epigenetic mechanism by which nutrition and aging can influence long-term health.
Asunto(s)
Envejecimiento/fisiología , Dieta , Elementos de Facilitación Genéticos , Epigénesis Genética , Factor Nuclear 4 del Hepatocito/genética , Islotes Pancreáticos/fisiología , Exposición Materna , Regiones Promotoras Genéticas , Animales , Línea Celular , Metilación de ADN , Femenino , Islotes Pancreáticos/citología , Ratas , Activación TranscripcionalRESUMEN
Investigations of memory mechanisms have been, thus far, neuron centric, despite the brain comprising diverse cell types. Using rats and mice, we assessed the cell-type-specific contribution of hippocampal insulin-like growth factor 2 (IGF2), a polypeptide regulated by learning and required for long-term memory formation. The highest level of hippocampal IGF2 was detected in pericytes, the multi-functional mural cells of the microvessels that regulate blood flow, vessel formation, the blood-brain barrier, and immune cell entry into the central nervous system. Learning significantly increased pericytic Igf2 expression in the hippocampus, particularly in the highly vascularized stratum lacunosum moleculare and stratum moleculare layers of the dentate gyrus. Igf2 increases required neuronal activity. Regulated hippocampal Igf2 knockout in pericytes, but not in fibroblasts or neurons, impaired long-term memories and blunted the learning-dependent increase of neuronal immediate early genes (IEGs). Thus, neuronal activity-driven signaling from pericytes to neurons via IGF2 is essential for long-term memory.
Asunto(s)
Neuronas , Pericitos , Animales , Ratones , Ratas , Hipocampo/metabolismo , Memoria a Largo Plazo , Neuronas/metabolismo , Transducción de SeñalRESUMEN
Maternal-offspring interactions in mammals involve both cooperation and conflict. The fetus has evolved ways to manipulate maternal physiology to enhance placental nutrient transfer, but the mechanisms involved remain unclear. The imprinted Igf2 gene is highly expressed in murine placental endocrine cells. Here, we show that Igf2 deletion in these cells impairs placental endocrine signaling to the mother, without affecting placental morphology. Igf2 controls placental hormone production, including prolactins, and is crucial to establish pregnancy-related insulin resistance and to partition nutrients to the fetus. Consequently, fetuses lacking placental endocrine Igf2 are growth restricted and hypoglycemic. Mechanistically, Igf2 controls protein synthesis and cellular energy homeostasis, actions dependent on the placental endocrine cell type. Igf2 loss also has additional long-lasting effects on offspring metabolism in adulthood. Our study provides compelling evidence for an intrinsic fetal manipulation system operating in placenta that modifies maternal metabolism and fetal resource allocation, with long-term consequences for offspring metabolic health.
Asunto(s)
Resistencia a la Insulina , Factor II del Crecimiento Similar a la Insulina , Placenta , Animales , Femenino , Ratones , Embarazo , Comunicación Celular , Homeostasis , Hipoglucemiantes , Factor II del Crecimiento Similar a la Insulina/genética , Impresión GenómicaRESUMEN
The healthy development of the fetus depends on an optimal balance between fetal genetic drive for growth and the maternal ability to provide nutrients through the placenta. Nothing is known about fetal-placental signaling in response to increased fetal demand in the situation of overgrowth. Here, we examined this question using the H19(Δ13) mouse model, shown previously to result in elevated levels of Igf2. Fetal and placental weights in H19(Δ13) were increased by 23% and 45%, respectively, at E19, when compared with wild-type mice. Unexpectedly, we found that disproportionately large H19(Δ13) placentas transport 20-35% less (per gram placenta) glucose and system A amino acids and have similar reductions in passive permeability, despite a significantly greater surface area for nutrient exchange and theoretical diffusion capacity compared with wild-type mice. Expression of key transporter genes Slc2a3 and Slc38a4 was reduced by â¼20%. Decreasing the overgrowth of the H19(Δ13) placenta by genetically reducing levels of Igf2P0 resulted in up-regulation of system A activity and maintenance of fetal overgrowth. Our results provide direct evidence that large placentas can modify their nutrient transfer capacity to regulate fetal nutrient acquisition. Our findings are indicative of fetal-placental signaling mechanisms that limit total demand for maternal nutrients.
Asunto(s)
Feto/metabolismo , Factor II del Crecimiento Similar a la Insulina/metabolismo , Animales , Femenino , Desarrollo Fetal/genética , Desarrollo Fetal/fisiología , Genotipo , Factor II del Crecimiento Similar a la Insulina/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Mutantes , Placenta/metabolismo , Embarazo , ARN Largo no Codificante , ARN no Traducido/genéticaRESUMEN
The placenta is a transient organ found in eutherian mammals that evolved primarily to provide nutrients for the developing fetus. The placenta exchanges a wide array of nutrients, endocrine signals, cytokines and growth factors with the mother and the fetus, thereby regulating intrauterine development. Recent studies show that the placenta is not just a passive organ mediating maternal-fetal exchange. It can adapt its capacity to supply nutrients in response to intrinsic and extrinsic variations in the maternal-fetal environment. These dynamic adaptations are thought to occur to maximize fetal growth and viability at birth in the prevailing conditions in utero. However, some of these adaptations may also affect the development of individual fetal tissues, with patho-physiological consequences long after birth. Here, this review summarizes current knowledge on the causes, possible mechanisms and consequences of placental adaptive responses, with a focus on the regulation of transporter-mediated processes for nutrients. This review also highlights the emerging roles that imprinted genes and epigenetic mechanisms of gene regulation may play in placental adaptations to the maternal-fetal environment.
Asunto(s)
Adaptación Fisiológica/fisiología , Desarrollo Fetal/fisiología , Intercambio Materno-Fetal/fisiología , Placenta/fisiología , Fenómenos Fisiologicos de la Nutrición Prenatal/fisiología , Aminoácidos/metabolismo , Animales , Calcio/metabolismo , Epigénesis Genética , Femenino , Feto/metabolismo , Ácido Fólico/metabolismo , Regulación del Desarrollo de la Expresión Génica , Impresión Genómica/fisiología , Edad Gestacional , Glucosa/metabolismo , Humanos , Embarazo , Transducción de SeñalRESUMEN
In the mouse, feto-placental endothelial cells (FPEC) line the inner surface of the feto-placental blood vessels located within placental labyrinthine zone and play critical roles in placental development and function. Here, we present a detailed protocol for isolation and culture of primary mouse FPEC, as well as two complementary methods (immunohistochemistry staining and flow cytometry analysis) to assess their purity. These cells are suitable for downstream ex vivo studies to investigate their functional properties, both in normal and pathological contexts. For complete details on the use and execution of this protocol, please refer to Sandovici et al. (2022).
Asunto(s)
Células Endoteliales , Placenta , Femenino , Embarazo , Animales , Ratones , Citometría de FlujoRESUMEN
Strong evidence suggests that early-life exposures to suboptimal environmental factors, including those in utero, influence our long-term metabolic health. This has been termed developmental programming. Mounting evidence suggests that the growth and metabolism of male and female fetuses differ. Therefore, sexual dimorphism in response to pre-conception or early-life exposures could contribute to known sex differences in susceptibility to poor metabolic health in adulthood. However, until recently, many studies, especially those in animal models, focused on a single sex, or, often in the case of studies performed during intrauterine development, did not report the sex of the animal at all. In this review, we (a) summarize the evidence that male and females respond differently to a suboptimal pre-conceptional or in utero environment, (b) explore the potential biological mechanisms that underlie these differences and (c) review the consequences of these differences for long-term metabolic health, including that of subsequent generations.
Asunto(s)
Caracteres Sexuales , Animales , Femenino , Masculino , FenotipoRESUMEN
In all eutherian mammals, growth of the fetus is dependent upon a functional placenta, but whether and how the latter adapts to putative fetal signals is currently unknown. Here, we demonstrate, through fetal, endothelial, hematopoietic, and trophoblast-specific genetic manipulations in the mouse, that endothelial and fetus-derived IGF2 is required for the continuous expansion of the feto-placental microvasculature in late pregnancy. The angiocrine effects of IGF2 on placental microvasculature expansion are mediated, in part, through IGF2R and angiopoietin-Tie2/TEK signaling. Additionally, IGF2 exerts IGF2R-ERK1/2-dependent pro-proliferative and angiogenic effects on primary feto-placental endothelial cells ex vivo. Endothelial and fetus-derived IGF2 also plays an important role in trophoblast morphogenesis, acting through Gcm1 and Synb. Thus, our study reveals a direct role for the imprinted Igf2-Igf2r axis on matching placental development to fetal growth and establishes the principle that hormone-like signals from the fetus play important roles in controlling placental microvasculature and trophoblast morphogenesis.
Asunto(s)
Factor II del Crecimiento Similar a la Insulina/metabolismo , Placenta/irrigación sanguínea , Receptor IGF Tipo 2/metabolismo , Animales , Línea Celular , Proteínas de Unión al ADN/genética , Células Endoteliales/metabolismo , Femenino , Desarrollo Fetal , Feto/metabolismo , Factor II del Crecimiento Similar a la Insulina/genética , Factor II del Crecimiento Similar a la Insulina/fisiología , Ratones , Ratones Endogámicos C57BL , Microvasos/metabolismo , Neovascularización Fisiológica/fisiología , Placenta/metabolismo , Placenta/fisiología , Placentación , Embarazo , Receptor IGF Tipo 2/fisiología , Factores de Transcripción/genética , Trofoblastos/metabolismoRESUMEN
Background: Obesity is a major risk factor for dysglycemic disorders, including type 2 diabetes (T2D). However, there is wide phenotypic variation in metabolic profiles. Tissue-specific epigenetic modifications could be partially accountable for the observed phenotypic variability. Scope: The aim of this systematic review was to summarize the available data on epigenetic signatures in human adipose tissue (AT) that characterize overweight or obesity-related insulin resistance (IR) and dysglycemia states and to identify potential underlying mechanisms through the use of unbiased bioinformatics approaches. Methods: Original data published in the last decade concerning the comparison of epigenetic marks in human AT of individuals with metabolically unhealthy overweight/obesity (MUHO) versus normal weight individuals or individuals with metabolically healthy overweight/obesity (MHO) was assessed. Furthermore, association of these epigenetic marks with IR/dysglycemic traits, including T2D, was compiled. Results: We catalogued more than two thousand differentially methylated regions (DMRs; above the cut-off of 5%) in the AT of individuals with MUHO compared to individuals with MHO. These DNA methylation changes were less likely to occur around the promoter regions and were enriched at loci implicated in intracellular signaling (signal transduction mediated by small GTPases, ERK1/2 signaling and intracellular trafficking). We also identified a network of seven transcription factors that may play an important role in targeting DNA methylation changes to specific genes in the AT of subjects with MUHO, contributing to the pathogeny of obesity-related IR/T2D. Furthermore, we found differentially methylated CpG sites at 8 genes that were present in AT and whole blood, suggesting that DMRs in whole blood could be potentially used as accessible biomarkers of MUHO. Conclusions: The overall evidence linking epigenetic alterations in key tissues such AT to metabolic complications in human obesity is still very limited, highlighting the need for further studies, particularly those focusing on epigenetic marks other than DNA methylation. Our initial analysis suggests that DNA methylation patterns can potentially discriminate between MUHO from MHO and provide new clues into why some people with obesity are less susceptible to dysglycemia. Identifying AT-specific epigenetic targets could also lead to novel approaches to modify the progression of individuals with obesity towards metabolic disease. Systematic Review Registration: PROSPERO, identifier CRD42021227237.
Asunto(s)
Tejido Adiposo/metabolismo , Enfermedades Metabólicas/genética , Obesidad/genética , Metilación de ADN , Epigénesis Genética , Histonas/metabolismo , HumanosRESUMEN
Genomic imprinting, an epigenetic phenomenon that causes the expression of a small set of genes in a parent-of-origin-specific manner, is thought to have co-evolved with placentation. Many imprinted genes are expressed in the placenta, where they play diverse roles related to development and nutrient supply function. However, only a small number of imprinted genes have been functionally tested for a role in nutrient transfer capacity in relation to the structural characteristics of the exchange labyrinthine zone. Here, we examine the transfer capacity in a mouse model deficient for the maternally expressed Phlda2 gene, which results in placental overgrowth and a transient reduction in fetal growth. Using stereology, we show that the morphology of the labyrinthine zone in Phlda2-/+ mutants is normal at E16 and E19. In vivo placental transfer of radiolabeled solutes 14C-methyl-D-glucose and 14C-MeAIB remains unaffected at both gestational time points. However, placental passive permeability, as measured using two inert hydrophilic solutes (14C-mannitol; 14C-inulin), is significantly higher in mutants. Importantly, this increase in passive permeability is associated with fetal catch-up growth. Our findings uncover a key role played by the imprinted Phlda2 gene in modifying placental passive permeability that may be important for determining fetal growth.
Asunto(s)
Intercambio Materno-Fetal , Proteínas Nucleares/genética , Placenta/metabolismo , 3-O-Metilglucosa/farmacocinética , Animales , Femenino , Eliminación de Gen , Impresión Genómica , Inulina/farmacocinética , Manitol/farmacocinética , Ratones , Ratones Endogámicos C57BL , Proteínas Nucleares/metabolismo , Embarazo , beta-Alanina/análogos & derivados , beta-Alanina/farmacocinéticaRESUMEN
When exposed to nutrient excess and insulin resistance, pancreatic ß-cells undergo adaptive changes in order to maintain glucose homeostasis. The role that growth control genes, highly expressed in early pancreas development, might exert in programming ß-cell plasticity in later life is a poorly studied area. The imprinted Igf2 (insulin-like growth factor 2) gene is highly transcribed during early life and has been identified in recent genome-wide association studies as a type 2 diabetes susceptibility gene in humans. Hence, here we investigate the long-term phenotypic metabolic consequences of conditional Igf2 deletion in pancreatic ß-cells (Igf2ßKO) in mice. We show that autocrine actions of IGF2 are not critical for ß-cell development, or for the early post-natal wave of ß-cell remodelling. Additionally, adult Igf2ßKO mice maintain glucose homeostasis when fed a chow diet. However, pregnant Igf2ßKO females become hyperglycemic and hyperinsulinemic, and their conceptuses exhibit hyperinsulinemia and placentomegalia. Insulin resistance induced by congenital leptin deficiency also renders Igf2ßKO females more hyperglycaemic compared to leptin-deficient controls. Upon high-fat diet feeding, Igf2ßKO females are less susceptible to develop insulin resistance. Based on these findings, we conclude that in female mice, autocrine actions of ß-cell IGF2 during early development determine their adaptive capacity in adult life.
Asunto(s)
Plasticidad de la Célula/fisiología , Factor II del Crecimiento Similar a la Insulina/fisiología , Células Secretoras de Insulina/citología , Animales , Femenino , Glucosa/metabolismo , Homeostasis , Insulina/sangre , Resistencia a la Insulina , Células Secretoras de Insulina/metabolismo , Masculino , Ratones , Ratones Noqueados , EmbarazoRESUMEN
Alterations in maternal physiological adaptation during pregnancy lead to complications, including abnormal birthweight and gestational diabetes. Maternal adaptations are driven by placental hormones, although the full identity of these is lacking. This study unbiasedly characterized the secretory output of mouse placental endocrine cells and examined whether these data could identify placental hormones important for determining pregnancy outcome in humans. Secretome and cell peptidome analyses were performed on cultured primary trophoblast and fluorescence-activated sorted endocrine trophoblasts from mice and a placental secretome map was generated. Proteins secreted from the placenta were detectable in the circulation of mice and showed a higher relative abundance in pregnancy. Bioinformatic analyses showed that placental secretome proteins are involved in metabolic, immune and growth modulation, are largely expressed by human placenta and several are dysregulated in pregnancy complications. Moreover, proof-of-concept studies found that secreted placental proteins (sFLT1/MIF and ANGPT2/MIF ratios) were increased in women prior to diagnosis of gestational diabetes. Thus, placental secretome analysis could lead to the identification of new placental biomarkers of pregnancy complications.
Asunto(s)
Placenta/metabolismo , Complicaciones del Embarazo/metabolismo , Proteoma/metabolismo , Animales , Células Cultivadas , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Placenta/citología , Embarazo , Complicaciones del Embarazo/genética , Proteoma/análisis , Proteoma/genética , Proteómica , Trofoblastos/citología , Trofoblastos/metabolismoRESUMEN
The islets of Langerhans are clusters of cells dispersed throughout the pancreas that produce several hormones essential for controlling a variety of metabolic processes, including glucose homeostasis and lipid metabolism. Studying the transcriptional control of pancreatic islet cells has important implications for understanding the mechanisms that control their normal development, as well as the pathogenesis of metabolic diseases such as diabetes. Histones represent the main protein components of the chromatin and undergo diverse covalent modifications that are very important for gene regulation. Here we describe the isolation of pancreatic islets from rodents and subsequently outline the methods used to immunoprecipitate and analyze the native chromatin obtained from these cells.
Asunto(s)
Inmunoprecipitación de Cromatina , Histonas/metabolismo , Islotes Pancreáticos/metabolismo , Procesamiento Proteico-Postraduccional , Animales , Separación Celular , Cromatina , Regulación de la Expresión Génica , Islotes Pancreáticos/citología , Ratones , Nucleosomas , Ratas , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Human recombination rates vary along the chromosomes as well as between the two sexes. There is growing evidence that epigenetic factors may have an important influence on recombination rates, as well as on crossover position. Using both public database analysis and wet-bench approaches, we revisited the relationship between increased rates of meiotic recombination and genome imprinting. We constructed metric linkage disequilibrium (LD) maps for all human chromosomal regions known to contain one or more imprinted genes. We show that imprinted regions contain significantly more LD units (LDU) and have significantly more haplotype blocks of smaller sizes than flanking nonimprinted regions. There is also an excess of hot-spots of recombination at imprinted regions, and this is likely to do with the presence of imprinted genes, per se. These findings indicate that imprinted chromosomal regions are historical "hot-spots" of recombination. We also demonstrate, by direct segregation analysis at the 11p15.5 imprinted region, that there is remarkable agreement between sites of meiotic recombination and steps in LD maps. Although the increase in LDU/Megabase at imprinted regions is not associated with any significant enrichment for any particular sequence class, major sequence determinants of recombination rates seem to differ between imprinted and control regions. Interestingly, fine-mapping of recombination events within the most male meiosis-specific recombination hot-spot of Chromosome 11p15.5 indicates that many events may occur within or directly adjacent to regions that are differentially methylated in somatic cells. Taken together, these findings support the involvement of a combination of specific DNA sequences and epigenetic factors as major determinants of hot-spots of recombination at imprinted chromosomal regions.
Asunto(s)
Cromosomas/ultraestructura , Impresión Genómica , Recombinación Genética , Islas de CpG , Metilación de ADN , Genoma , Humanos , Modelos Lineales , Desequilibrio de Ligamiento , Modelos Genéticos , Familia de MultigenesRESUMEN
Tissue-specific stem cells have unique properties and growth requirements, but a small set of juxtacrine and paracrine signals have been identified that are required across multiple niches. Whereas insulin-like growth factor II (IGF-II) is necessary for prenatal growth, its role in adult stem cell physiology is largely unknown. We show that loss of Igf2 in adult mice resulted in a â¼50% reduction in slowly dividing, label-retaining cells in the two regions of the brain that harbor neural stem cells. Concordantly, induced Igf2 deletion increased newly generated neurons in the olfactory bulb accompanied by hyposmia, and caused impairments in learning and memory and increased anxiety. Induced Igf2 deletion also resulted in rapid loss of stem and progenitor cells in the crypts of Lieberkühn, leading to body-weight loss and lethality and the inability to produce organoids in vitro. These data demonstrate that IGF-II is critical for multiple adult stem cell niches.