Imprinted genes and mother-offspring interactions

The parenting hub of the hypothalamus is a focus of imprinted gene action

Imprinted genes are subject to germline epigenetic modification resulting in parental-specific allelic silencing. Although genomic imprinting is thought to be important for maternal behaviour, this idea is based on serendipitous findings from a small number of imprinted genes. Here, we undertook an unbiased systems biology approach, taking advantage of the recent delineation of specific neuronal populations responsible for controlling parental care, to test whether imprinted genes significantly converge to regulate parenting behaviour. Using single-cell RNA sequencing datasets, we identified a specific enrichment of imprinted gene expression in a recognised "parenting hub", the galanin-expressing neurons of the preoptic area. We tested the validity of linking enriched expression in these neurons to function by focusing on MAGE family member L2 (Magel2), an imprinted gene not previously linked to parenting behaviour. We confirmed expression of Magel2 in the preoptic area galanin expressing neurons. We then examined the parenting behaviour of Magel2-null(+/p) mice. Magel2-null mothers, fathers and virgin females demonstrated deficits in pup retrieval, nest building and pup-directed motivation, identifying a central role for this gene in parenting. Finally, we show that Magel2-null mothers and fathers have a significant reduction in POA galanin expressing cells, which in turn contributes to a reduced c-Fos response in the POA upon exposure to pups. Our findings identify a novel imprinted gene that impacts parenting behaviour and, moreover, demonstrates the utility of using single-cell RNA sequencing data to predict gene function from expression and in doing so here, have identified a purposeful role for genomic imprinting in mediating parental behaviour.

Sperm DNA methylome abnormalities occur both pre- and post-treatment in men with Hodgkin disease and testicular cancer

BACKGROUND

Combination chemotherapy has contributed to increased survival from Hodgkin disease (HD) and testicular cancer (TC). However, questions concerning the quality of spermatozoa after treatment have arisen. While studies have shown evidence of DNA damage and aneuploidy in spermatozoa years following anticancer treatment, the sperm epigenome has received little attention. Our objectives here were to determine the impact of HD and TC, as well as their treatments, on sperm DNA methylation. Semen samples were collected from community controls (CC) and from men undergoing treatment for HD or TC, both before initiation of chemotherapy and at multiple times post-treatment. Sperm DNA methylation was assessed using genome-wide and locus-specific approaches.

RESULTS

Imprinted gene methylation was not affected in the sperm of HD or TC men, before or after treatment. Prior to treatment, using Illumina HumanMethylation450 BeadChip (450 K) arrays, a subset of 500 probes was able to distinguish sperm samples from TC, HD and CC subjects; differences between groups persisted post-treatment. Comparing altered sperm methylation between HD or TC patients versus CC men, twice as many sites were affected in TC versus HD men; for both groups, the most affected CpGs were hypomethylated. For TC patients, the promoter region of GDF2 contained the largest region of differential methylation. To assess alterations in DNA methylation over time/post-chemotherapy, serial samples from individual patients were compared. With restriction landmark genome scanning and 450 K array analyses, some patients who underwent chemotherapy showed increased alterations in DNA methylation, up to 2 to 3 years post-treatment, when compared to the CC cohort. Similarly, a higher-resolution human sperm-specific assay that includes assessment of environmentally sensitive regions, or "dynamic sites," also demonstrated persistently altered sperm DNA methylation in cancer patients post-treatment and suggested preferential susceptibility of "dynamic" CpG sites.

CONCLUSIONS

Distinct sperm DNA methylation signatures were present pre-treatment in men with HD and TC and may help explain increases in birth defects reported in recent clinical studies. Epigenetic defects in spermatozoa of some cancer survivors were evident even up to 2 years post-treatment. Abnormalities in the sperm epigenome both pre- and post-chemotherapy may contribute to detrimental effects on future reproductive health.

Fetal Growth and Intrauterine Epigenetic Programming of Obesity and Cardiometabolic Disease

Epidemiologic studies have shown an association between an adverse intrauterine environment (eg, exposure to malnutrition) and an increased risk of developing cardiometabolic disease in adulthood. These studies laid the foundation for the developmental origins of health and disease hypothesis, which states that limited nutrient supply to the fetus results in physiologic and metabolic adaptations that favor survival but result in unfavorable consequences in the offspring if there is excess nutrition after birth. This discrepancy in the pre- and postnatal milieus, perceived as stress by the offspring, may confer an increased risk of developing cardiometabolic disease later in life. Thus, early life exposures result in programming or changes in cellular memory that have effects on health throughout the life course. One of the mechanisms by which programming occurs is via epigenetic modifications of genes, processes that result in functionally relevant changes in genes (ie, gene expression) without an alteration in the genotype. In this review, we will describe how fetal exposures, including under- and overnutrition, affect neonatal and childhood growth and the future risk for cardiometabolic disease.

Role of Maternal Infections and Inflammatory Responses on Craniofacial Development

Pregnancy is a tightly regulated immunological state. Mild environmental perturbations can affect the developing fetus significantly. Infections can elicit severe immunological cascades in the mother's body as well as the developing fetus. Maternal infections and resulting inflammatory responses can mediate epigenetic changes in the fetal genome, depending on the developmental stage. The craniofacial development begins at the early stages of embryogenesis. In this review, we will discuss the immunology of pregnancy and its responsive mechanisms on maternal infections. Further, we will also discuss the epigenetic effects of pathogens, their metabolites and resulting inflammatory responses on the fetus with a special focus on craniofacial development. Understanding the pathophysiological mechanisms of infections and dysregulated inflammatory responses during prenatal development could provide better insights into the origins of craniofacial birth defects.

Alteration of Genomic Imprinting after Assisted Reproductive Technologies and Long-Term Health

Assisted reproductive technologies (ART) are the treatment of choice for some infertile couples and even though these procedures are generally considered safe, children conceived by ART have shown higher reported risks of some perinatal and postnatal complications such as low birth weight, preterm birth, and childhood cancer. In addition, the frequency of some congenital imprinting disorders, like Beckwith-Wiedemann Syndrome and Silver-Russell Syndrome, is higher than expected in the general population after ART. Experimental evidence from animal studies suggests that ART can induce stress in the embryo and influence gene expression and DNA methylation. Human epigenome studies have generally revealed an enrichment of alterations in imprinted regions in children conceived by ART, but no global methylation alterations. ART procedures occur simultaneously with the establishment and maintenance of imprinting during embryonic development, so this may underlie the apparent sensitivity of imprinted regions to ART. The impact in adulthood of imprinting alterations that occurred during early embryonic development is still unclear, but some experimental evidence in mice showed higher risk to obesity and cardiovascular disease after the restriction of some imprinted genes in early embryonic development. This supports the hypothesis that imprinting alterations in early development might induce epigenetic programming of metabolism and affect long-term health. Given the growing use of ART, it is important to determine the impact of ART in genomic imprinting and long-term health.

DNA Methylation and gene expression patterns are widely altered in fetal growth restriction and associated with FGR development

Fetal growth restriction (FGR) is the failure of the fetus toachieve its genetically determined growth potential, which increasesrisks for a variety of genetic diseases, such as type 2 diabetes mellitus, coronary artery disease, and stroke, during the lifetime. The dysregulation of DNA methylationis known to interact with environmental fluctuations, affect gene expressions comprehensively, and be fatal to fetus development in specific cases. Therefore, we set out to find out epigenetic and transcriptomic alterations associated with FGR development. We found a set of differentially expressed genes associated with differentially methylated regions in placentae and cord blood samples. Using dimensional reduction analysis, the expression and methylation variables of the epigenetically altered genes classified the FGR samples from the controls. These genes were also enriched in the biological pathways such as metabolism and developmental processes related to FGR. Furthermore, three genes of INS, MEG3, and ZFP36L2 are implicated in epigenetic imprinting, which has been associated with FGR. These results strongly suggest that DNA methylation is highly dysregulated during FGR development, and abnormal DNA methylation patterns are likely to alter gene expression.

Imprinting aberrations of SNRPN, ZAC1 and INPP5F genes involved in the pathogenesis of congenital heart disease with extracardiac malformations

Congenital heart disease (CHD) with extracardiac malformations (EM) is the most common multiple malformation, resulting from the interaction between genetic abnormalities and environmental factors. Most studies have attributed the causes of CHD with EM to chromosomal abnormalities. However, multi‐system dysplasia is usually caused by both genetic mutations and epigenetic dysregulation. The epigenetic mechanisms underlying the pathogenesis of CHD with EM remain unclear. In this study, we investigated the mechanisms of imprinting alterations, including those of the Small nuclear ribonucleoprotein polypeptide N (SNRPN), PLAG1 like zinc finger 1 (ZAC1) and inositol polyphosphate‐5‐phosphatase F (INPP5F) genes, in the pathogenesis of CHD with EM. The methylation levels of SNRPN, ZAC1, and INPP5F genes were analysed by the MassARRAY platform in 24 children with CHD with EM and 20 healthy controls. The expression levels of these genes were detected by real‐time polymerase chain reaction (PCR). The correlation between methylation regulation and gene expression was confirmed using 5‐azacytidine (5‐Aza) treated cells. The methylation levels of SNRPN and ZAC1 genes were significantly increased in CHD with EM, while that of INPP5F was decreased. The methylation alterations of these genes were negatively correlated with expression. Risk analysis showed that abnormal hypermethylation of SNRPN and ZAC1 resulted in 5.545 and 7.438 times higher risks of CHD with EM, respectively, and the abnormal hypomethylation of INPP5F was 8.38 times higher than that of the control group. We concluded that abnormally high methylation levels of SNRPN and ZAC1 and decreased levels of INPP5F imply an increased risk of CHD with EM by altering their gene functions. This study provides evidence of imprinted regulation in the pathogenesis of multiple malformations.

Placental volume and other first-trimester outcomes: are there differences between fresh embryo transfer, frozen-thawed embryo transfer and natural conception?

RESEARCH QUESTION

Does mode of conception influence placental volume and other first-trimester outcomes?

DESIGN

This retrospective single-centre case-control study led in Dijon University Hospital included 252 singleton pregnancies (84 IVF with either fresh embryo transfer or frozen-thawed embryo transfer [FET] and 168 natural conceptions). First-trimester placental volume, uterine artery pulsatility index and maternal serum PAPP-A and beta-HCG were measured. Statistical analyses were adjusted for gestational age, the newborn's gender, maternal age, parity, body mass index and smoking status.

RESULTS

Placental volume was significantly greater in the FET group than in the control group (P = 0.043) and fresh embryo transfer (P = 0.023) groups. At birth, fresh embryo transfer newborns were significantly smaller than controls (P = 0.01) and FET newborns (P = 0.008). Postpartum haemorrhage was far more frequent in FET than in controls and fresh embryo transfer group (38.1%, 2.6% and 1.9%, respectively; P < 0.0001). Placental volume positively correlated with PAPP-A, beta-HCG and the newborn's birth weight, and negatively correlated with uterine artery pulsatility index.

CONCLUSIONS

Placental volume and other first-trimester parameters are modified by IVF with fresh embryo transfer and FET compared with natural conception, but with opposite trends. Given the different protocols used for these techniques, hormonal treatment per se may have a major effect on pregnancy outcomes through the modification of placental invasiveness.

Maternal stress and early-onset colorectal cancer

Early-onset colorectal cancer (EOCRC) is defined as colorectal cancer (CRC) diagnosed before the age of 50. Alarmingly, there has been a significant increase in EOCRC diagnoses' worldwide over the past several decades. Emerging data suggest EOCRCs have distinguishing clinical, pathological, biological and molecular features; and thus, are a fundamentally different subtype of CRCs. Unfortunately, there is no simple explanation for the causes of EOCRC. Scientifically rigorous studies are needed to determine what may be driving the challenging epidemiology of EOCRC. We contend here that a reasonable hypothesis is that prenatal risk factors such as maternal stress and associated sleeping disorders influence offspring epigenetic make-up, and shape immune system and gut health contributing to an increased risk for EOCRC.

Altered GNAS imprinting due to folic acid deficiency contributes to poor embryo development and may lead to neural tube defects

Disturbed epigenetic modifications have been linked to the pathogenesis of Neural Tube Defects (NTDs) in those with folate deficiency during pregnancy. However, evidence is lacking to delineate the critical region in epigenome regulated by parental folic acid and mechanisms by which folate deficiency affects normal embryogenesis. Our data from clinical samples revealed the presence of aberrant DNA methylation in GNAS imprinting cluster in NTD samples with low folate concentrations. Results from mouse models indicated that the establishment of GNAS imprinting was influenced by both maternal and paternal folate-deficient diets. Such aberrant GNAS imprinting was present prior to the gametogenesis period. Imprinting in Exon1A/GNAS gDMR was abolished in both spermatozoa and oocytes upon treating with a parental folate-deficient diet (3.6% in spermatozoa, 9.8% in oocytes). Interestingly, loss of imprinting in the GNAS gene cluster altered chromatin structure to an overwhelmingly open structure (58.48% in the folate-free medium group vs. 39.51% in the folate-normal medium group; P < 0.05), and led to a disturbed expression of genes in this region. Furthermore, an elevated cyclic AMP levels was observed in folate acid deficiency group. Our results imply that GNAS imprinting plays major roles in folic acid metabolism regulation during embryogenesis. Aberrant GNAS imprinting is an attribute to NTDs, providing a new perspective for explaining the molecular mechanisms by which folate supplementation in human pregnancy provides protection from NTDs.

Differences between NMRI and DBA/2J mice in the development of somites and susceptibility to methylnitrosourea-induced skeleton anomalies

The development of DBA/2J mouse strain embryos is nearly 12 h - or 6 somite pairs - delayed as compared to the outbred NMRI mouse embryos of the same age on gestation days (GD) 8-12. To evaluate inter-strain differences in susceptibility to teratogens, dams were treated with methylnitrosourea (MNU, 5 mg/kg body weight i.p.) on defined gestation days (NMRI: GD 9, 91/2 or 10; DBA/2J: GD 10 or 101/2). Skeletal anomalies produced by MNU on both mouse strains varied with the GD of treatment. The pattern of anomalies produced by MNU on a given GD markedly differed between the two mouse strains, yet they were similar -with a few exceptions- when exposures at equivalent embryonic stages are compared. Findings from this study indicated that strain-dependent differences in the developmental stage of mouse embryos of the same gestational age occur, a possibility that has been often neglected when inter-strain differences in susceptibility to developmental toxicants are interpreted.

Gene-environment interaction influences attachment-like style in mice

Attachment styles are established soon after birth and form the basis for a healthy psychological life during adulthood. Here, we investigated whether genetic background (i.e. isogenic strains: C57BL/6N and BALB/c) and parent-of-origin (i.e. reciprocal hybrids) epigenetic effects influence attachment-like styles in mice. We discovered that a specific genetic and epigenetic assortment exerts a role on the development of a secure or insecure attachment-like style. In particular, when biological mothers raise their pups, the attachment-like style is mainly secure, independently of the genetic background. However, when foster mothers raise pups, the attachment-like style can be either secure or insecure, depending on the particular genetic background, and this effect is paternally transmitted. Finally, we observed that secure attachment-like in mice leads to greater sociability during adulthood, while insecure attachment-like leads to reduced sociability. Our study sheds light on gene-environment interactions that shape the attachment-like style early in development and pave the way for a healthy psychological life.

Genome-wide random regression analysis for parent-of-origin effects of body composition allometries in mouse

Genomic imprinting underlying growth and development traits has been recognized, with a focus on the form of absolute or pure growth. However, little is known about the effect of genomic imprinting on relative growth. In this study, we proposed a random regression model to estimate genome-wide imprinting effects on the relative growth of multiple tissues and organs to body weight in mice. Joint static allometry scaling equation as sub-model is nested within the genetic effects of markers and polygenic effects caused by a pedigree. Both chromosome-wide and genome-wide statistical tests were conducted to identify imprinted quantitative trait nucleotides (QTNs) associated with relative growth of individual tissues and organs to body weight. Real data analysis showed that three of six analysed tissues and organs are significantly associated with body weight in terms of phenotypic relative growth. At the chromosome-wide level, a total 122 QTNs were associated with allometries of kidney, spleen and liver weights to body weight, 36 of which were imprinted with different imprinting fashions. Further, only two imprinted QTNs responsible for relative growth of spleen and liver were verified by genome-wide test. Our approach provides a general framework for statistical inference of genomic imprinting underlying allometry scaling in animals.

Detection of imprinting effects for qualitative traits on X chromosome based on nuclear families

Methods for detecting imprinting effects have been developed primarily for autosomal markers. However, no method is available in the literature to test for imprinting effects on X chromosome. Therefore, it is necessary to suggest methods for detecting such imprinting effects. In this article, the parental-asymmetry test on X chromosome (XPAT) is first developed to test for imprinting for qualitative traits in the presence of association, based on family trios each with both parents and their affected daughter. Then, we propose 1-XPAT to deal with parent-daughter pairs, each with one parent and his/her affected daughter. By simultaneously considering family trios and parent-daughter pairs, C-XPAT (the combined test statistic of XPAT and 1-XPAT) is constructed to test for imprinting. Further, we extend the proposed methods to accommodate complete (with both parents) and incomplete (with one parent) nuclear families having multiple daughters of which at least one is affected. Simulation results demonstrate that the proposed methods control the size well, irrespective of the inbreeding coefficient in females being zero or non-zero. By incorporating incomplete nuclear families, C-XPAT is more powerful than XPAT using only complete nuclear families. For practical use, these proposed methods are applied to analyse the rheumatoid arthritis data and Turner's syndrome data.

Epigenetic legacy of parental experiences: Dynamic and interactive pathways to inheritance

The quality of the environment experienced by an individual across his or her lifespan can result in a unique developmental trajectory with consequences for adult phenotype and reproductive success. However, it is also evident that these experiences can impact the development of offspring with continued effect on subsequent generations. Epigenetic mechanisms have been proposed as a mediator of both these within- and across-generation effects, and there is increasing evidence to support the role of environmentally induced changes in DNA methylation, posttranslational histone modifications, and noncoding RNAs in predicting these outcomes. Advances in our understanding of these molecular modifications contribute to increasingly nuanced perspectives on plasticity and transmission of phenotypes across generations. A challenge that emerges from this research is in how we integrate these "new" perspectives with traditional views of development, reproduction, and inheritance. This paper will highlight evidence suggestive of an epigenetic impact of the environment on mothers, fathers, and their offspring, and illustrate the importance of considering the dynamic nature of reproduction and development and inclusive views of inheritance within the evolving field of behavioral and environmental epigenetics.

Methods of epigenome editing for probing the function of genomic imprinting

The curious patterns of imprinted gene expression draw interest from several scientific disciplines to the functional consequences of genomic imprinting. Methods of probing the function of imprinting itself have largely been indirect and correlational, relying heavily on conventional transgenics. Recently, the burgeoning field of epigenome editing has provided new tools and suggested strategies for asking causal questions with site specificity. This perspective article aims to outline how these new methods may be applied to questions of functional imprinting and, with this aim in mind, to suggest new dimensions for the expansion of these epigenome-editing tools.

15q11.2 Duplication Encompassing Only the UBE3A Gene Is Associated with Developmental Delay and Neuropsychiatric Phenotypes

Duplications of chromosome region 15q11-q13 with the maternal imprint are associated with a wide spectrum of neuropsychiatric disorders, including autism spectrum disorders, developmental delay, learning difficulties, schizophrenia, and seizures. These observations suggest there is a dosage-sensitive imprinted gene or genes within this region that explains the increased risk for neuropsychiatric phenotypes. We present a female patient with developmental delay in whom we identified a maternally inherited 129-Kb duplication in chromosome region 15q11.2 encompassing only the UBE3A gene. Expression analysis in cultured fibroblasts confirmed overexpression of UBE3A in the proband, compared with age- and sex-matched controls. We further tested segregation of this duplication in four generations and found it segregated with neuropsychiatric phenotypes. Our study shows for the first time clinical features associated with overexpression of UBE3A in humans and underscores the significance of this gene in the phenotype of individuals with 15q11-q13 duplication.

The placenta: phenotypic and epigenetic modifications induced by Assisted Reproductive Technologies throughout pregnancy

Today, there is growing interest in the potential epigenetic risk related to assisted reproductive technologies (ART). Much evidence in the literature supports the hypothesis that adverse pregnancy outcomes linked to ART are associated with abnormal trophoblastic invasion. The aim of this review is to investigate the relationship between epigenetic dysregulation caused by ART and subsequent placental response. The dialogue between the endometrium and the embryo is a crucial step to achieve successful trophoblastic invasion, thus ensuring a non-complicated pregnancy and healthy offspring. However, as described in this review, ART could impair both actors involved in this dialogue. First, ART may induce epigenetic defects in the conceptus by modifying the embryo environment. Second, as a result of hormone treatments, ART may impair endometrial receptivity. In some cases, it results in embryonic growth arrest but, when the development of the embryo continues, the placenta could bring adaptive responses throughout pregnancy. Amongst the different mechanisms, epigenetics, especially thanks to a finely tuned network of imprinted genes stimulated by foetal signals, may modify nutrient transfer, placental growth and vascularization. If these coping mechanisms are overwhelmed, improper maternal-foetal exchanges occur, potentially leading to adverse pregnancy outcomes such as abortion, preeclampsia or intra-uterine growth restriction. But in most cases, successful placental adaptation enables normal progress of the pregnancy. Nevertheless, the risks induced by these modifications during pregnancy are not fully understood. Metabolic diseases later in life could be exacerbated through the memory of epigenetic adaptation mechanisms established during pregnancy. Thus, more research is still needed to better understand abnormal interactions between the embryo and the milieu in artificial conditions. As trophectoderm cells are in direct contact with the environment, they deserve to be studied in more detail. The ultimate goal of these studies will be to render ART protocols safer. Optimization of the environment will be the key to improving the dialogue between the endometrium and embryo, so as to ensure that placentation after ART is similar to that following natural conception.

Prenatal exposure to systemic antibacterials and overweight and obesity in Danish schoolchildren: a prevalence study

BACKGROUND/OBJECTIVE

Prenatal exposure to antibacterials may permanently dysregulate fetal metabolic patterns via epigenetic pathways or by altering maternal microbiota. We examined the association of prenatal exposure to systemic antibacterials with overweight and obesity in schoolchildren.

SUBJECTS/METHODS

We conducted a prevalence study among Danish schoolchildren aged 7-16 years using data from routine school anthropometric evaluations conducted during 2002-2013. Prenatal exposure to antibacterials was ascertained by using maternal prescription dispensations and infection-related hospital admissions during pregnancy. We defined overweight and obesity among the children using standard age- and sex-specific cutoffs. We computed sex-specific adjusted prevalence ratios (aPRs) of overweight and obesity associated with exposure to prenatal antibacterials, adjusting for maternal age at delivery, marital status, smoking in pregnancy and multiple gestation; we also stratified the analyses by birth weight.

RESULTS

Among 9886 schoolchildren, 3280 (33%) had prenatal exposure to antibacterials. aPRs associated with the exposure were 1.26 (95% confidence interval (CI): 1.10-1.45) for overweight and 1.29 (95% CI: 1.03-1.62) for obesity. Among girls, aPRs were 1.16 (95% CI: 0.95-1.42) for overweight and 1.27 (95% CI: 0.89 to 1.82) for obesity. Among boys, aPRs were 1.37 (95% CI: 1.13-1.66) for overweight and 1.29 (95% CI: 0.96-1.73) for obesity. The aPR for overweight was higher among schoolchildren with birth weight <3500 g (aPR: 1.30, 95% CI: 1.05-1.61) than in schoolchildren with birth weight ⩾3500 g (aPR: 1.18, 95% CI: 0.95-1.46). Inversely, the association for obesity was higher among schoolchildren with birth weight ⩾3500 g (aPR: 1.35, 95% CI: 1.00-1.81) than among those who were <3500 g at birth (aPR: 1.16, 95% CI: 0.82-1.65).

CONCLUSIONS

Prenatal exposure to systemic antibacterials is associated with an increased risk of overweight and obesity at school age, and this association varies by birth weight.

Genomic conflicts and sexual antagonism in human health: insights from oxytocin and testosterone

We review the hypothesized and observed effects of two of the major forms of genomic conflicts, genomic imprinting and sexual antagonism, on human health. We focus on phenotypes mediated by peptide and steroid hormones (especially oxytocin and testosterone) because such hormones centrally mediate patterns of physical and behavioral resource allocation that underlie both forms of conflict. In early development, a suite of imprinted genes modulates the human oxytocinergic system as predicted from theory, with paternally inherited gene expression associated with higher oxytocin production, and increased solicitation to mothers by infants. This system is predicted to impact health through the incompatibility of paternal-gene and maternal-gene optima and increased vulnerability of imprinted gene systems to genetic and epigenetic changes. Early alterations to oxytocinergic systems have long-term negative impacts on human psychological health, especially through their effects on attachment and social behavior. In contrast to genomic imprinting, which generates maladaptation along an axis of mother–infant attachment, sexual antagonism is predicted from theory to generate maladaptation along an axis of sexual dimorphism, modulated by steroid and peptide hormones. We describe evidence of sexual antagonism from studies of humans and other animals, demonstrating that sexually antagonistic effects on sex-dimorphic phenotypes, including aspects of immunity, life history, psychology, and behavior, are commonly observed and lead to forms of maladaptation that are demonstrated, or expected, to impact human health. Recent epidemiological and psychiatric studies of schizophrenia in particular indicate that it is mediated, in part, by sexually antagonistic alleles. The primary implication of this review is that data collection focused on (i) effects of imprinted genes that modulate the oxytocin system, and (ii) effects of sexually antagonistic alleles on sex-dimorphic, disease-related phenotypes will lead to novel insights into both human health and the evolutionary dynamics of genomic conflicts.

Association of the intronic polymorphism rs12540874 A>G of the GRB10 gene with high birth weight

BACKGROUND

High birth weight (HBW) is considered a key predictor of the development of chronic diseases, such as Type 2 Diabetes (T2D). Foetal growth depends on many factors, among which placental function is critical. Some genes with expression in the placenta, such as GRB10, are known to be involved in the regulation of insulin receptor pathways and the size of mouse littermates.

AIM

To evaluate whether the intronic polymorphism rs12540874 A>G of the GRB10 gene is associated with HBW in term newborns.

STUDY DESIGN

A total of 51 healthy term newborns were enrolled in a nested case-control study. The case group was defined by the presence of HBW (n=17) and the control group by newborns with normal birth weight (NBW n=34). Maternal and foetal factors influencing HBW were considered as exclusion criteria. The polymorphism was determined through real-time PCR using TaqMan technology. Categorical variables were evaluated with descriptive statistics, and multivariate logistic regression analysis was used to evaluate the association between polymorphism and HBW.

RESULTS

The newborns in the case group had a longer gestation period (39. 7 ± 1.0 and 38.8 ± 1.8 weeks) and higher insulin levels at birth (9.5 ± 4.0 and 5.7 ± 3.4 μU/mL) than the newborns in the control group. The multivariate regression analysis, adjusted for weeks of gestation, showed a significant association between the SNP rs12540874 A>G of the GRB10 gene with HBW (OR 4.9; CI95% 1.10-22.10 p=0.02).

CONCLUSIONS

Our results suggest that the SNP rs12540874 A>G, an intronic SNP of the gene GRB10, is associated with HBW.

Human in vitro oocyte maturation is not associated with increased imprinting error rates at LIT1, SNRPN, PEG3 and GTL2

STUDY QUESTION

Does in vitro maturation (IVM) of cumulus-enclosed germinal vesicle (GV) stage oocytes retrieved from small antral follicles in minimally stimulated cycles without an ovulatory hCG dose induce imprinting errors at LIT1, SNRPN, PEG3 and GTL2 in human oocytes?

SUMMARY ANSWER

There is no significant increase in imprinting mutations at LIT1, SNRPN, PEG3 and GTL2 after IVM of cumulus-enclosed GV oocytes from small antral follicles in minimally stimulated cycles without hCG priming.

WHAT IS KNOWN ALREADY

Animal models have generally demonstrated correct methylation imprint establishment for in vitro grown and matured oocytes. For human IVM, well-designed studies allowing conclusions on imprint establishment are currently not available.

STUDY DESIGN, SIZE, DURATION

Immature oocyte-cumulus complexes from 2 to 9 mm follicles were retrieved in polycystic ovary syndrome (PCOS) subjects in minimally stimulated cycles without hCG priming and matured in vitro. In vivo grown oocytes were retrieved after conventional ovarian stimulation for IVF/ICSI or after ovulation induction. Imprinting error rates at three maternally methylated (LIT1, SNRPN and PEG3) and one paternally methylated (GTL2) imprinted genes were compared in 71 in vitro and 38 in vivo matured oocytes.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The limiting dilution bisulfite sequencing technique was applied, allowing increased sensitivity based on multiplex PCR for the imprinted genes and the inclusion of non-imprinted marker genes for cumulus cell DNA contamination.

MAIN RESULTS AND THE ROLE OF CHANCE

In vitro as well as in vivo matured oocytes showed only a few abnormal alleles, consistent with epimutations. The abnormalities were more frequent in immature than in mature oocytes for both groups, although no significant difference was reached. There was no statistically significant increase in imprinting errors in IVM oocytes.

LIMITATIONS, REASONS FOR CAUTION

This single cell methylation analysis was restricted to a number of well-selected imprinted genes. Genome-wide methylation analysis of single human oocytes is currently not possible.

WIDER IMPLICATIONS OF THE FINDINGS

IVM is a patient-friendly alternative to conventional ovarian stimulation in PCOS patients and is associated with reduced gonadotrophin costs and avoidance of OHSS. The results of this study show for the first time that optimized human IVM procedures have no significant effects on the establishment of maternal DNA methylation patterns at LIT1, SNRPN, PEG3 and GTL2.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by research funds from Agentschap voor Innovatie door Wetenschap en Technologie (IWT-TBM 110680), Wetenschappelijk Fonds Willy Gepts (WFWG 2011) and German Research Foundation (HA 1374/12-2). There are no competing interests.

Modulation of imprinted gene expression following superovulation

Although assisted reproductive technologies increase the risk of low birth weight and genomic imprinting disorders, the precise underlying causes remain unclear. Using a mouse model, we previously showed that superovulation alters the expression of imprinted genes in the placenta at 9.5days (E9.5) of gestation. Here, we investigate whether effects of superovulation on genomic imprinting persisted at later stages of development and assess the surviving fetuses for growth and morphological abnormalities. Superovulation, followed by embryo transfer at E3.5, as compared to spontaneous ovulation (controls), resulted in embryos of normal size and weight at 14.5 and 18.5days of gestation. The normal monoallelic expression of the imprinted genes H19, Snrpn and Kcnq1ot1 was unaffected in either the placentae or the embryos from the superovulated females at E14.5 or E18.5. However, for the paternally expressed imprinted gene Igf2, superovulation generated placentae with reduced production of the mature protein at E9.5 and significantly more variable mRNA levels at E14.5. We propose that superovulation results in the ovulation of abnormal oocytes with altered expression of imprinted genes, but that the coregulated genes of the imprinted gene network result in modulated expression.

Statistical dissection of cyto-nuclear epistasis subject to genomic imprinting in line crosses

Cytoplasm contains important metabolism reaction organelles such as mitochondria and chloroplast (in plant). In particular, mitochondria contains special DNA information which can be passed to offsprings through maternal gametes, and has been confirmed to play a pivotal role in nuclear activities. Experimental evidences have documented the importance of cyto-nuclear interactions in affecting important biological traits. While studies have also pointed out the role of interaction between imprinting nuclear DNA and cytoplasm, no statistical method has been developed to efficiently model such effect and further quantify its effect size. In this work, we developed an efficient statistical model for genome-wide estimating and testing the cytoplasmic effect, nuclear DNA imprinting effect as well as the interaction between them under reciprocal backcross and F2 designs derived from inbred lines. Parameters are estimated under maximum likelihood framework implemented with the EM algorithm. Extensive simulations show good performance in a variety of scenarios. The utility of the method is demonstrated by analyzing a published data set in an F2 family derived from C3H/HeJBir and C57BL/6 J mouse strains. Important cyto-nuclear interactions were identified. Our approach provides a quantitative framework for identifying and estimating cyto-nuclear interactions subject to genomic imprinting involved in the genetic control of complex traits.

Dosage-sensitivity of imprinted genes expressed in the brain: 15q11-q13 and neuropsychiatric illness

Imprinted genes, those genes subject to parent-of-origin-specific epigenetic marking resulting in monoallelic parent-specific expression, are sensitive to subtle changes in expression dosage. This has been illustrated in a number of experimental models and the fact that both decreased (or complete loss) and increased imprinted gene expression can lead to human diseases. In the present paper, we discuss the consequence of increased dosage of imprinted genes for brain function, focusing on the PWS (Prader-Willi syndrome) locus on human chromosome 15q11-q13 and how predicted increases in dosage of maternally expressed imprinted genes from this interval are associated with a higher risk of developing psychotic illness. The evidence for this comes from individuals with PWS itself and also non-syndromic cases of psychosis in carriers of a maternally derived copy number variant spanning this locus. Of the known imprinted genes in this region, the prime candidate is maternally expressed UBE3A, which encodes E6-AP (E6-associated protein) ubiquitin ligase and has an influence on a number of important neurotransmitter systems. Furthermore, these findings point to the fact that brain function is exquisitely sensitive to both decreases and increases in the expression of imprinted genes.

Brain-expressed imprinted genes and adult behaviour: the example of Nesp and Grb10

Imprinted genes are defined by their parent-of-origin-specific monoallelic expression. Although the epigenetic mechanisms regulating imprinted gene expression have been widely studied, their functional importance is still unclear. Imprinted genes are associated with a number of physiologies, including placental function and foetal growth, energy homeostasis, and brain and behaviour. This review focuses on genomic imprinting in the brain and on two imprinted genes in particular, Nesp and paternal Grb10, which, when manipulated in animals, have been shown to influence adult behaviour. These two genes are of particular interest as they are expressed in discrete and overlapping neural regions, recognised as key "imprinting hot spots" in the brain. Furthermore, these two genes do not appear to influence placental function and/or maternal provisioning of offspring. Consequently, by understanding their behavioural function we may begin to shed light on the evolutionary significance of imprinted genes in the adult brain, independent of the recognised role in maternal care. In addition, we discuss the potential future directions of research investigating the function of these two genes and the behavioural role of imprinted genes more generally.

Selective inbreeding does not increase gut microbiota similarity in BALB/c mice

Inflammatory diseases in mouse models are under strong impact from the gut microbiota. Therefore increased interindividual gut microbiota similarity may be seen as a way to reduce group sizes in mouse experiments. The composition of the gut microbiota is to a high extent defined by genetics, and it is known that selecting siblings as mothers even in inbred colonies may increase the gut microbiota similarity among the mice with 3-4%. We therefore hypothesized that selective breeding of mice aiming at a high similarity in the gut microbiota would increase the interindividual similarity of the gut microbiota. BALB/cCrl mice were, however, found to have a mean heterozygosity of only 0.8% in their genome, and selection of breeders with a high similarity in the gut microbiota for three generations did not change the overall gut microbiota similarity, which was 66% in the P generation and 66%, 64% and 63% in the F1, F2 and F3 generations, respectively. Increased gut microbiota similarity in closely related mice in inbred mouse colonies is, therefore, more likely to be caused by other factors, such as imprinting or different intrauterine conditions, rather than by residual heterozygosity.

Parametric proportional hazards model for mapping genomic imprinting of survival traits

A number of imprinted genes have been observed in plants, animals and humans. They not only control growth and developmental traits, but may also be responsible for survival traits. Based on the Cox proportional hazards (PH) model, we constructed a general parametric model for dissecting genomic imprinting, in which a baseline hazard function is selectable for fitting the effects of imprinted quantitative trait loci (iQTL) genotypes on the survival curve. The expectation-maximisation (EM) algorithm is derived for solving the maximum likelihood estimates of iQTL parameters. The imprinting patterns of the detected iQTL are statistically tested under a series of null hypotheses. The Bayesian information criterion (BIC) model selection criterion is employed to choose an optimal baseline hazard function with maximum likelihood and parsimonious parameterisation. We applied the proposed approach to analyse the published data in an F(2) population of mice and concluded that, among five commonly used survival distributions, the log-logistic distribution is the optimal baseline hazard function for the survival time of hyperoxic acute lung injury (HALI). Under this optimal model, five QTL were detected, among which four are imprinted in different imprinting patterns.

Placental development during early pregnancy in sheep: effects of embryo origin on fetal and placental growth and global methylation

The origin of embryos including those created through assisted reproductive technologies might have profound effects on placental and fetal development, possibly leading to compromised pregnancies associated with poor placental development. To determine the effects of embryo origin on fetal size, and maternal and fetal placental cellular proliferation and global methylation, pregnancies were achieved through natural mating (NAT), or transfer of embryos generated through in vivo (NAT-ET), IVF, or in vitro activation (IVA). On Day 22 of pregnancy, fetuses were measured and placental tissues were collected to immunologically detect Ki67 (a marker of proliferating cells) and 5-methyl cytosine followed by image analysis, and determine mRNA expression for three DNA methyltransferases. Fetal length and labeling index (proportion of proliferating cells) in maternal caruncles (maternal placenta) and fetal membranes (fetal placenta) were less (P < 0.001) in NAT-ET, IVF, and IVA than in NAT. In fetal membranes, expression of 5-methyl cytosine was greater (P < 0.02) in IVF and IVA than in NAT. In maternal caruncles, mRNA expression for DNMT1 was greater (P < 0.01) in IVA compared with the other groups, but DNMT3A expression was less (P < 0.04) in NAT-ET and IVA than in NAT. In fetal membranes, expression of mRNA for DNMT3A was greater (P < 0.01) in IVA compared with the other groups, and was similar in NAT, NAT-ET, and IVF groups. Thus, embryo origin might have specific effects on growth and function of ovine uteroplacental and fetal tissues through regulation of tissue growth, DNA methylation, and likely other mechanisms. These data provide a foundation for determining expression of specific factors regulating placental and fetal tissue growth and function in normal and compromised pregnancies, including those achieved with assisted reproductive technologies.

dsPIG: a tool to predict imprinted genes from the deep sequencing of whole transcriptomes

Background

Dysregulation of imprinted genes, which are expressed in a parent-of-origin-specific manner, plays an important role in various human diseases, such as cancer and behavioral disorder. To date, however, fewer than 100 imprinted genes have been identified in the human genome. The recent availability of high-throughput technology makes it possible to have large-scale prediction of imprinted genes. Here we propose a Bayesian model (dsPIG) to predict imprinted genes on the basis of allelic expression observed in mRNA-Seq data of independent human tissues.

Results

Our model (dsPIG) was capable of identifying imprinted genes with high sensitivity and specificity and a low false discovery rate when the number of sequenced tissue samples was fairly large, according to simulations. By applying dsPIG to the mRNA-Seq data, we predicted 94 imprinted genes in 20 cerebellum samples and 57 imprinted genes in 9 diverse tissue samples with expected low false discovery rates. We also assessed dsPIG using previously validated imprinted and non-imprinted genes. With simulations, we further analyzed how imbalanced allelic expression of non-imprinted genes or different minor allele frequencies affected the predictions of dsPIG. Interestingly, we found that, among biallelically expressed genes, at least 18 genes expressed significantly more transcripts from one allele than the other among different individuals and tissues.

Conclusion

With the prevalence of the mRNA-Seq technology, dsPIG has become a useful tool for analysis of allelic expression and large-scale prediction of imprinted genes. For ease of use, we have set up a web service and also provided an R package for dsPIG at http://www.shoudanliang.com/dsPIG/.

Elevated expression of PEG10 in human placentas from preeclamptic pregnancies

The aim of this study was to determine qualitative and quantitative changes in paternally expressed gene 10 (PEG10) expression in preeclamptic placentas. Placental tissues were obtained immediately after delivery from women with normal pregnancies (n=20) and patients with preeclampsia (n=20). Quantitative real-time RT-PCR, Western blot analysis and immunohistochemistry were used to determine PEG10 gene expression and localization in placental tissues. Compared with the normal group, PEG10 was highly expressed at both mRNA and protein levels in preeclampsia (P<0.05). In immunohistochemical staining, PEG10 was present in the syncytiotrophoblast, cytotrophoblast, endothelial cell and stroma of all placentas. Notably, the intensity of PEG10 expression in the syncytiotrophoblast, cytotrophoblast and stem villi was much higher in preeclampsia than in normal. In conclusion, elevated expression of PEG10 is likely to be involved in the pathophysiology of preeclampsia. Further studies are needed to elucidate the precise role of PEG10 in preeclampsia.

Conservation of genomic imprinting at the NDN, MAGEL2 and MEST loci in pigs

Imprinted genes have important effects on the regulation of fetal growth, development, and postnatal behavior. However, the study of imprinted genes has been limited in mammalian species other than human and mouse. Therefore, the study of porcine imprinted genes is useful for defining the extent of conservation of genomic imprinting among different species. In this study, the imprinting status of porcine NDN, MAGEL2 and MEST genes was determined by direct sequencing of the cDNAs and detection of single nucleotide polymorphisms (SNPs) identified in individuals from reciprocal crosses between Meishan and Large White pigs for allele discrimination. The analysis was carried out in 13 different tissues (skeletal muscle, fat, pituitary gland, heart, lung, liver, kidney, spleen, stomach, small intestine, uterus, ovary and testis) from 12 two-month-old piglets. Imprinting analysis showed that NDN and MAGEL2 were paternally expressed in all tissues where the genes were expressed as in human and mouse. Interestingly, MEST showed tissue-specific imprinting, being paternally expressed in skeletal muscle, fat, pituitary gland, heart, kidney, lung, stomach and uterus, and maternally expressed in spleen and liver.

Bayesian mapping of genome-wide epistatic imprinted loci for quantitative traits

Genomic imprinting, an epigenetic phenomenon of parent-of-origin-specific gene expression, has been widely observed in plants, animals, and humans. To detect imprinting genes influencing quantitative traits, the least squares and maximum likelihood approaches for fitting a single quantitative trait locus (QTL) and Bayesian methods for simultaneously modeling multiple QTL have been adopted, respectively, in various studies. However, most of these studies have only estimated imprinting main effects and thus ignored imprinting epistatic effects. In the presence of extremely complex genomic imprinting architectures, we introduce a Bayesian model selection method to analyze the multiple interacting imprinted QTL (iQTL) model. This approach will greatly enhance the computational efficiency through setting the upper bound of the number of QTLs and performing selective sampling for QTL parameters. The imprinting types of detected main-effect QTLs can be estimated from the Bayes factor statistic formulated by the posterior probabilities for the genetic effects being compared. The performance of the proposed method is demonstrated by several simulation experiments. Moreover, this method is applied to dissect the imprinting genetic architecture for body weight in mouse and fruit weight in tomato. Matlab code for implementing this approach will be available from the authors upon request.

Epigenetics and microRNAs in preeclampsia

Strong evidence suggests a potential link among epigenetics, microRNAs (miRNAs), and pregnancy complications. Much research still needs to be carried out to determine whether epigenetic factors are predictive in the pathogenesis of preeclampsia (PE), a life-threatening disease during pregnancy. Recently, the importance of maternal epigenetic features, including DNA methylation, histone modifications, epigenetically regulated miRNA, and the effect of imprinted or non-imprinted genes on trophoblast growth, invasion, as well as fetal development and hypertension in pregnancy, has been demonstrated in a series of articles. This article discusses the current evidence of this complicated network of miRNA and epigenetic factors as potential mechanisms that may underlie the theories of disease for PE. Translating these basic epigenetic findings to clinical practice could potentially serve as prognostic biomarkers for diagnosis in its early stages and could help in the development of prophylactic strategies.

Sexual conflict in primates

Sexual conflict is increasingly recognized as a major force for evolutionary change and holds great potential for delineating variation in primate behavior and morphology. The goals of this review are to highlight the rapidly rising field of sexual conflict and the ongoing shift in our understanding of interactions between the sexes. We discuss the evidence for sexual conflict within the Order Primates, and assess how studies of primates have illuminated and can continue to increase our understanding of sexual conflict and sexual selection. Finally, we introduce a framework for understanding the behavioral, anatomical, and genetic expression of sexual conflict across primate mating systems and suggest directions for future research.

Association of SLC38A4 and system A with abnormal fetal birth weight

In this study, we aimed to explore the correlation between solute carrier family 38 member 4 (SLC38A4) and system A activity in human placentas from pregnancies with abnormal fetal birth weight. We collected placentas from consenting women immediately after their full-term babies were born, with normal, low birth weight or macrosomia, and used real-time PCR and Western blot analysis to detect the levels of SLC38A4 mRNA and protein [also known as sodium-coupled neutral amino acid transport protein 4 (SNAT4)]. Isotope incorporation assay was applied to measure system A activity in the placentas. Compared to the normal birth weight (NBW) group, placentas from the fetal macrosomia (FM) group had significantly increased levels of SLC38A4 mRNA and SNAT4 (both were increased by almost 2-fold; P<0.05), while no significant changes were detected in the placentas from the low birth weight (LBW) group. In addition, system A activity in the placentas from the FM and LBW groups was significantly different from that in the NBW group (1.2±0.20, 0.6±0.14 vs. 1.0±0.18, P<0.05). The data suggest that SNAT4 and system A have a strong association with abnormal fetal birth weight and that they may play a crucial role in fetal growth and development.

Molecular cloning, mRNA expression and imprinting status of PEG3, NAP1L5 and PPP1R9A genes in pig

Imprinted genes are expressed monoallelically depending on their parental origin, and play important roles in the regulation of fetal growth, development, and postnatal behavior. Most genes known to be imprinted have been identified and studied in the human and the mouse. However, there are only a small number of reported imprinted genes in pigs. Therefore, identification and characterization of more imprinted genes in pigs is useful for comparative analysis of genomic imprinting across species. In this study, we cloned the porcine PEG3, NAP1L5 and PPP1R9A genes. The imprinting status of these genes was determined using sequencing directly and single nucleotide polymorphisms (SNPs) identified in individuals from reciprocal cross of Meishan and Large White pigs. Imprinting analysis was carried out in 13 different tissues (skeletal muscle, fat, pituitary gland, heart, lung, liver, kidney, spleen, stomach, small intestine, uterus, ovary and testis) from twelve 2-month-old piglets. Imprinting analysis showed that PEG3 and NAP1L5 were exclusively expressed from the paternal allele whereas PPP1R9A was biallelically expressed in all tissues tested where the genes were expressed. The study is of interest to understand the conservation of genomic imprinting among mammals at the 3 loci.

Genome Scan for Parent-of-Origin QTL Effects on Bovine Growth and Carcass Traits

Parent-of-origin effects (POE) such as genomic imprinting influence growth and body composition in livestock, rodents, and humans. Here, we report the results of a genome scan to detect quantitative trait loci (QTL) with POE on growth and carcass traits in Angus × Brahman cattle crossbreds. We identified 24 POE–QTL on 15 Bos taurus autosomes (BTAs) of which six were significant at 5% genome-wide (GW) level and 18 at the 5% chromosome-wide (CW) significance level. Six QTL were paternally expressed while 15 were maternally expressed. Three QTL influencing post-weaning growth map to the proximal end of BTA2 (linkage region of 0–9 cM; genomic region of 5.0–10.8 Mb), for which only one imprinted ortholog is known so far in the human and mouse genomes, and therefore may potentially represent a novel imprinted region. The detected QTL individually explained 1.4 ∼ 5.1% of each trait’s phenotypic variance. Comparative in silico analysis of bovine genomic locations show that 32 out of 1,442 known mammalian imprinted genes from human and mouse homologs map to the identified QTL regions. Although several of the 32 genes have been associated with quantitative traits in cattle, only two (GNAS and PEG3) have experimental proof of being imprinted in cattle. These results lend additional support to recent reports that POE on quantitative traits in mammals may be more common than previously thought, and strengthen the need to identify and experimentally validate cattle orthologs of imprinted genes so as to investigate their effects on quantitative traits.

Imprinting and expression analysis of a non-coding RNA gene in the mouse Dlk1-Dio3 domain

The Dlk1-Dio3 imprinted domain not only is implicated growth and development of the embryo and placenta, but also affects adult metabolism and brain function. In this study, we identified the imprinting status of a mouse non-coding RNA gene, B830012L14Rik, mapped to the Dlk1-Dio3 domain by the polymorphism- and sequencing-based approach. Imprinting analysis showed that the gene was expressed maternally at E15.5, E18.5 and postnatal day 1 mice. Two transcripts of approximately 1.9 and 3.5 kb were detected by northern blot. Furthermore, we examined the spatiotemporal expression patterns of the gene during the mouse development. In situ hybridization analysis showed that B830012L14Rik was mainly expressed in forebrain, pituitary, cartilage primordium of spinal column, lung and liver at E13.5 and E15.5. The results of real-time quantitative RT-PCR showed that the B830012L14Rik expression in brain, heart, lung and liver was higher at E15.5 than at E12.5 and E18.5. Furthermore, the gene expression increased progressively in brain from E12.5 to E15.5 whereas decreased from E15.5 to E19.5. This study may provide further insights into the imprinting, genomic features and expression regulation of the Dlk1-Dio3 imprinted cluster.

Imprinting analysis of porcine MAGEL2 gene in two fetal stages and association analysis with carcass traits

Imprinted genes play an essential role in the regulation of fetal growth, development and function of the placenta, however only a limited number of imprinted genes have been studied in swine. In this study, we cloned and characterized porcine MAGEL2 (melanoma antigen-like gene 2), and also identified its imprinting status during porcine fetal development. The complete open reading frame (ORF) encoding 1,193 amino acids was isolated and two single nucleotide polymorphisms (SNPs) (g.2592A>C and g.3277T>C) in the coding region were identified. The reciprocal Yorkshire×Meishan F1 hybrid model and the RT-PCR/RFLP method were used to detect the imprinting status of porcine MAGEL2 gene at two developmental stages of day 30 and 65 of gestation. Imprinting analysis showed that porcine MAGEL2 was paternally expressed in day 65 fetal tissues, including heart, liver, spleen, lung, kidney, stomach, small intestine, skeletal muscle, brain and placenta. Interestingly, we observed an imprinting variance of MAGEL2 gene in 30 dpc fetuses produced by the cross of Yorkshire boar×Meishan sow, in which seven heterozygous fetuses were monoallelically expressed from the paternal allele but two were biallelically expressed from both the paternal and maternal alleles. Association analysis in a Yorkshire×Meishan F2 resource population showed that the mutation of g.2592A>C was significantly associated with dressed carcass percentage (P<0.05) and buttock fat thickness (P<0.05). Our results suggest that MAGEL2, as a novel imprinted gene in pig, might be a candidate gene affecting carcass traits and could provide important information for the functional study of imprinted genes during porcine development.