Assisted reproductive technology is today considered a safe and reliable medical intervention, with healthy live births a reality for many IVF and ICSI treatment cycles. However, there are increasing numbers of published reports describing epigenetic/imprinting anomalies in children born as a result of these procedures. These anomalies have been attributed to methylation errors in embryo chromatin remodelling during in vitro culture. Here we re-visit three concepts: (1) the so-called ‘in vitro toxicity’ of ‘essential amino acids’ before the maternal to zygotic transition period; (2) the effect of hyperstimulation (controlled ovarian hyperstimulation) on homocysteine in the oocyte environment and the effect on methylation in the absence of essential amino acids; and (3) the fact/postulate that during the early stages of development the embryo undergoes a ‘global’ demethylation. Methylation processes require efficient protection against oxidative stress, which jeopardizes the correct acquisition of methylation marks as well as subsequent methylation maintenance. The universal precursor of methylation [by S-adenosyl methionine (SAM)], methionine, ‘an essential amino acid’, should be present in the culture. Polyamines, regulators of methylation, require SAM and arginine for their syntheses. Cystine, another ‘semi-essential amino acid’, is the precursor of the universal protective antioxidant molecule: glutathione. It protects methylation marks against some undue DNA demethylation processes through ten-eleven translocation (TET), after formation of hydroxymethyl cytosine. Early embryos are unable to convert homocysteine to cysteine as the cystathionine β-synthase pathway is not active. In this way, cysteine is a ‘real essential amino acid’. Most IVF culture medium do not maintain methylation/epigenetic processes, even in mouse assays. Essential amino acids should be present in human IVF medium to maintain adequate epigenetic marking in preimplantation embryos. Furthermore, morphological and morphometric data need to be re-evaluated, taking into account the basic biochemical processes involved in early life.

Imprinted genes uniquely drive and support fetoplacental growth by controlling the allocation of maternal resources to the fetus and affecting the newborn’s growth. We previously showed that alterations of the placental imprinted gene expression are associated with suboptimal perinatal growth and respond to environmental stimuli including socio-economic determinants. At the same time, maternal psychosocial stress during pregnancy (MPSP) has been shown to affect fetal growth. Here, we set out to test the hypothesis that placental imprinted gene expression mediates the effects of MPSP on fetal growth in a well-characterized birth cohort, the Stress in Pregnancy (SIP) Study. We observed that mothers experiencing high MPSP deliver infants with lower birthweight (P=0.047). Among the 109 imprinted genes tested, we detected panels of placental imprinted gene expression of 23 imprinted genes associated with MPSP and 26 with birthweight. Among these genes, five imprinted genes (CPXM2, glucosidase alpha acid (GAA), GPR1, SH3 and multiple ankyrin repeat domains 2 (SHANK2) and THSD7A) were common to the two panels. In multivariate analyses, controlling for maternal age and education and gestational age at birth and infant gender, two genes, GAA and SHANK2, each showed a 22% mediation of MPSP on fetal growth. These data provide new insights into the role that imprinted genes play in translating the maternal stress message into a fetoplacental growth pattern.

A well-known feature of the great H1N1 influenza pandemic of a century ago is that the highest mortality rate was amongst young adults. The general explanation has been that they died from an over-reaction of their active immune systems. This explanation has never been very satisfactory because teenagers also have very active immune systems. Recent virological research provides a new perspective, which is important for life and health insurers. There is now strong recent scientific evidence for the principle of antigenic imprinting, where the highest antibody response is against influenza virus strains from childhood. The peak ages of 1918 pandemic mortality correspond to a cohort exposed to the H3N8 1889–1890 Russian influenza pandemic. The vulnerability of an individual depends crucially on his or her exposure to influenza during their lifetime, especially childhood. Date of birth is thus a key indicator of pandemic vulnerability. An analysis of the implications is presented, with focus on those now in their fifties, who were exposed to the H3N2 1968 Hong Kong influenza.

An experiment of a 2×2 full diallelic cross between two contemporary Iberian pig strains (Retinto: RR, and Torbiscal: TT) was conducted to estimate the crossbreeding effects for growth and carcass traits. Phenotypic records were obtained under intensive management and consisted of two different data sets. The first set comprised growth traits until weaning and was collected at two different farms (6236 and 1208 records, respectively). Specific data included individual piglet weight at birth and at weaning at 28 days and average daily gain from birth to weaning at 28 days (ADG28) for both RR and TT and their reciprocal crosses. The second set comprised growth data from birth to slaughter (~340 days and ~160 kg) and carcass traits from 349 individuals (randomly) sampled at weaning from the first dataset. Data were analyzed through a Bayesian analysis by using a reparameterization of Dickerson’s model that allowed estimation of the posterior distributions of the following crossbreeding effects: average maternal breed effect (gM), average paternal breed effect (gP) and individual heterosis (hI). Results showed that the relative magnitude of crossbreeding effects depends on the trait analyzed. Crosses where Torbiscal strain was used as mother (RT and TT) achieved the greatest performance for all growth traits at weaning, leading to remarkable gM effects. The most outstanding example is the case of ADG28 where the probability of relevance was one. In contrast, TR cross showed the greatest differences from RR cross for all growth at slaughter and carcass traits. These differences were mainly due to hI and gP crossbreeding parameters. In particular, the posterior mean of hI was more noticeable for live weight at slaughter, average daily gain at slaughter and carcass length, while gP was more relevant for hams (kg) and loins (kg) representing from 3% to10% of average performance of traits. Hence, growth traits at weaning did not reveal any notable advantage of the crossbreeding scheme because of the superiority of the Torbiscal strain with respect to its mothering ability and the small hI. However, results from growth and carcass traits at slaughter would support the implementation of a TR crossbred system. It would allow exploitation of both the gP of the Torbiscal strain and the hI between these two Iberian pig strains. Additionally, gP estimates and phenotypic differences between reciprocal crosses might suggest signs of the presence of paternal genetic imprinting in primal cuts traits.

Young workers, experimentally removed from their nest and set in front of it, are not very good at finding the nest entrance and entering the nest. I examined how young ants learn their nest entrance characteristics, dealing only with the entrance sensu stricto, not with its vicinity. I observed that young ants have the innate behavior of trying to exit and re-enter their nest. I found that they are imprinted with the nest entrance odor while they are still living inside their nest and that they learn the visual aspect of their nest entrances, thanks to operant conditioning, when they exit their nest and succeed in re-entering in the course of their first short trips outside.

Imprinting control regions (ICRs) play a fundamental role in establishing and maintaining the non-random monoallelic expression of certain genes, via common regulatory elements such as non-coding RNAs and differentially methylated regions (DMRs) of DNA. We recently surveyed DNA methylation levels within four ICRs (H19-ICR, IGF2-DMR, KvDMR, and NESPAS-ICR) in whole-blood genomic DNA from 128 monozygotic (MZ) and 128 dizygotic (DZ) human twin pairs. Our analyses revealed high individual variation and intra-domain covariation in methylation levels across CpGs and emphasized the interaction between epigenetic variation and the underlying genetic sequence in a parent-of-origin fashion. Here, we extend our analysis to conduct two genome-wide screenings of single nucleotide polymorphisms (SNPs) underlying either intra-domain covariation or parent-of-origin-dependent association with methylation status at individual CpG sites located within ICRs. Although genome-wide significance was not surpassed due to sample size limitations, the most significantly associated SNPs found through multiple-trait genome-wide association (MQFAM) included the previously described rs10732516, which is located in the vicinity of the H19-ICR. Similarly, we identified an association between rs965808 and methylation status within the NESPAS-ICR. This SNP is positioned within an intronic region of the overlapping genes GNAS and GNAS-AS1, which are imprinted genes regulated by the NESPAS-ICR. Sixteen other SNPs located in regions apart from the analyzed regions displayed suggestive association with intra-domain methylation. Additionally, we identified 13 SNPs displaying parent-of-origin association with individual methylation sites through family-based association testing. In this exploratory study, we show the value and feasibility of using alternative GWAS approaches in the study of the interaction between epigenetic state and genetic sequence within imprinting regulatory domains. Despite the relatively small sample size, we identified a number of SNPs displaying suggestive association either in a domain-wide or in a parent-of-origin fashion. Nevertheless, these associations will require future experimental validation or replication in larger and independent samples.

Early feeding experiences, e.g. related to milk feeding, can affect later food and taste preferences. However, consequences of breast-feeding on taste acceptance are under-investigated. The objective of the present study was to examine the impact of exclusive breast-feeding duration (DEB) on taste acceptance at 6 and 12 months in the same infants (n 122). Mothers recorded the DEB. Acceptance of solutions of each of the five basic tastes relative to water was evaluated in the laboratory at 6 and 12 months by the ingestion ratio (IR). Kendall correlations were calculated between the DEB and the IR. Only 16 % completed at least 6 months of exclusive breast-feeding; 79 % had begun complementary feeding by 6 months. At 6 months, infants preferred sweet, salty and umami solutions over water and were indifferent to sour and bitter solutions. The longer an infant was breast-fed, the more s/he accepted the umami solution at 6 months. At 12 months, infants preferred sweet and salty solutions over water and were indifferent to sour, bitter and umami solutions. The relationship between the DEB and acceptance of the umami solution was not observed at 12 months. No relationship was observed between the DEB and sweet, salty, sour and bitter taste acceptance at 6 or 12 months. The association between the DEB and umami taste acceptance at 6 months may relate to the higher glutamate content of human milk compared with formula milk. Beyond the acknowledged metabolic benefits of breast-feeding, this suggests that prolonged breast-feeding could also be associated with an impact on sensory preference at the beginning of complementary feeding.

To evaluate the integrity of genomic imprinting in embryos that failed to develop normally following intracytoplasmic sperm injection (ICSI), we analysed the methylation profile of H19 and KCNQ1OT1 imprinting control regions, H19DMR and KvDMR1 respectively, in high-grade blastocysts and in embryos that exhibited developmental anomalies. Significant hypomethylation of KvDMR1 was specifically observed in 5/5 atypical blastocysts graded BC, which probably reflected the vulnerability of the imprint in the inner cell mass during the methylation remodelling phase in the early embryo. In addition, KvDMR1 was hypermethylated in 2/5 CC graded atypical blastocysts and in 2/8 embryos that exhibited developmental delay. H19DMR appeared differentially methylated in all groups of embryos. DNA methyltransfersase 1 (DNMT1) expression was similar in most of the tested embryos and could not account for the abnormal methylation patterns of KvDMR1 observed.

The Darwin theory of evolution by natural selection is based on three principles: (a) variation; (b) inheritance; and (c) natural selection. Here, I take these principles as an excuse to review some topics related to the future research prospects in Animal Breeding. With respect to the first principle I describe two forms of variation different from mutation that are becoming increasingly important: variation in copy number and microRNAs. With respect to the second principle I comment on the possible relevance of non-mendelian inheritance, the so-called epigenetic effects, of which the genomic imprinting is the best characterized in domestic species. Regarding selection principle I emphasize the importance of selection for social traits and how this could contribute to both productivity and animal welfare. Finally, I analyse the impact of molecular biology in Animal Breeding, the achievements and limitations of quantitative trait locus and classical marker-assisted selection and the future of genomic selection.

Genetic (or ‘genomic’) imprinting, a feature of approximately 100 mammalian genes, results in monoallelic expression from one of the two parentally inherited chromosomes. To date, most studies have been directed on imprinted genes in murine or human models; however, there is burgeoning interest in the effects of imprinted genes in domestic livestock species. In particular, attention has focused on imprinted genes that influence foetal growth and development and that are associated with several economically important production traits in cattle, sheep and pigs. We have re-sequenced regions in 20 candidate bovine imprinted genes in order to validate single nucleotide polymorphisms (SNPs) that may influence important production traits in cattle. Putative SNPs detected via re-sequencing were subsequently re-formatted for high-throughput SNP genotyping in 185 cattle samples comprising 138 performance-tested European Bos taurus (all Limousin bulls), 29 African B. taurus and 18 Indian B. indicus samples. Analysis of the resulting genotypic data identified 117 validated SNPs. Preliminary genotype–phenotype association analyses using 83 SNPs that were polymorphic in the Limousin samples with minor allele frequencies ⩾0.05 revealed significant associations between two candidate bovine imprinted genes and a range of important beef production traits: average daily gain, average feed intake, live weight, feed conversion ratio, residual feed intake and residual gain. These genes were the Ras protein-specific guanine nucleotide releasing factor gene (RASGRF1) and the zinc finger, imprinted 2 gene (ZIM2). Despite the relatively small sample size used in these analyses, the observed associations with production traits are supported by the purported biological function of the RASGRF1 and ZIM2 gene products. These results support the hypothesis that imprinted genes contribute significantly to important complex production traits in cattle. Furthermore, these SNPs may be usefully incorporated into future marker-assisted and genomic selection breeding schemes.

This critical appraisal of contemporary interpretations in the area of infantile attachment begins with an outline of the principal features of the Bowlby-Ainsworth ethological theory, the instrumental/operant learning theory of Gewirtz, and Hoffman's classical conditioning model. Some attention is also given to Cairns's contiguity learning analysis and the Hoffman-Solomon opponentprocess model Discussion of these theories is followed by a review of representative data from infants at four phyletic levels (precocial birds, dogs, monkeys, and human beings), with an emphasis on three aspects of social bonding: (a) the formation and persistence of social ties in the infant under conditions of maltreatment, (b) the role of the attachment object in the adjustment of the infant to the broader environment (the so-called secure base effect), and (c) the infant's reaction to involuntary separation from the attachment object.

An attempt is made to judge how well each of the interpretations accounts for all or part of the data, with the conclusion that current theories do not accord completely with documented attachment phenomena. The following criticisms are highlighted: Ethological theory emphasizes that infants' behavior systems have been shaped by the ordinarily expectable environment and depend on that environment for their functioning, yet infants of many species form bonds to objects not typical in any species' environment, or even to sources of maltreatment. Learning theory is faulted for making predictions contradicted by the maltreatment data and for a lack of formal mechanisms to account for the secure base and separation effects. The contiguity analysis is criticized for its inability to account for the emergence of certain response patterns during separation, and the opponent-process model is called into question because of its failure to fit important affective dynamics of social separation (a central focus of this theory). Recommendations for future theories of attachment are offered.

Much clinical and ethnographic evidence suggests that humans, like many other organisms, are selected to avoid close inbreeding because of the fitness costs of inbreeding depression. The proximate mechanism of human inbreeding avoidance seems to be precultural, and to involve the interaction of genetic predispositions and environmental conditions. As first suggested by E. Westermarck, and supported by evidence from Israeli kibbutzim, Chinese sim-pua marriage, and much convergent ethnographic and clinical evidence, humans negatively imprint on intimate associates during a critical period of early childhood (between ages 2 and 6).

There is also much evidence that, like other social animals, humans do not seek to maximize outbreeding, but rather to maintain an optimal balance between outbreeding and inbreeding. Close inbreeding reduces fitness through inbreeding depression, but some inbreeding brings the benefits of nepotism. For simple, stateless, horticultural societies, the optimal balance seems to be achieved by a combination of precultural inbreeding avoidance of relatives with an r ≤·25 and cultural rules of preferential marriage with kin with r ≥·25. Adjustment of the coefficient of inbreeding to other ecological settings seems to be largely cultural. An interactive model of “culture in nature” is presented, in which culture is seen as coevolving with genes to produce the maxiniization of individual inclusive fitness.

DNA methylation is one of the proposed biochemical mechanisms involved in cell differentiation and in genomic imprinting, and DNA methyltransferase (DMT) is a key enzyme in the embryo since mutation of its gene is lethal early in development. In order to verify that non-viability of uniparental embryos was not due to a defect in the regulation of DMT activity, we compared the metabolism of methylation in parthenogenetic embryos (maternal genome) and in fertilised embryos (maternal and paternal genomes). As regards total methylation, estimated by a measure of S-adenosyl methionine (SAM) and S-adenosyl homocysteine (SAH) formation, no significant difference was found between the two kinds of embryos during preimplantation development. Mean values were 4.5 ± 0.6 fmol (SAM +SAH)/h per 2-cell embryo and 0.40 ± 0.05 fmol SAH/h per 2-cell embryo, i.e. a SAH/(SAM + SAH) ratio of 9%; there was no detectable SAH formation in blastocysts. The same observation can be made for DMT activity, with mean values of: 7.8 fmol/h per oocyte, 8.5 fmol/h per 2-cell embryo, 6.1 fmol/h per 4-cell embryo, 4.1 fmol/h per morula, and no detectable activity in blastocysts. Total methylation as well as DNA methylation is characterised by a progressive drop in activity during preimplantation development.

The review addresses the fundamental process of ‘imprinting’. In his classical studies on newly hatched goslings Konrad Lorenz analysed the development of social binding and established the term ‘imprinting’ to describe this process. One of his major ideas was that imprinting occurs in ‘critical periods’, which are limited and severely restricted to the animal's very early life. For some time past, the term ‘imprinting’ is also used for an epigenetic mechanism, the ‘genomic imprinting’, which can be simply defined as gamete-of-origin dependent modification of genotype. Furthermore, in the course of the perinatal period ‘imprinting’ of physiological control systems occurs. Functional systems of the organism develop from open loop systems without feedback control into closed systems controlled by feedback mechanism. During ‘critical periods’, the actual environment influences the development of the respective physiological control systems for the entire life period, especially by changes in neuroorganization and expression of related effector genes. On the one hand, these mechanisms may cause perinatal malprogramming, which has been related to, e.g., metabolic disorders and cardiovascular diseases during later life in humans as well as in animals. On the other hand, knowledge on these mechanisms might be specifically used to induce long-term adaptation of the organism, for instance, to the postnatal climatic conditions (epigenetic temperature adaptation). Furthermore, the question if ‘critical period’ and ‘sensitive period’ are synonymous or different, and problems of identifying these developmental windows are discussed. Environmental manipulation of immature physiological mechanisms may be a physiological tool for characterization of ‘critical periods’.

Assisted reproductive techniques (ARTs) have been widely used over the past two decades to help infertile couples conceive. Recent studies on the ART-conceived population have raised concern about the possible risks of these techniques, in particular with regard to increased incidence of growth and developmental disorders. Some of these effects might be linked to genomic imprinting defects, although current evidence does not allow definite conclusions to be drawn. This review summarises studies that have examined effects of gamete and embryo manipulations on imprinted genes, and discusses the evidence for and against effects of ARTs on offspring health, and in particular imprinting-related conditions.