Male killers and the origins of paternal genome elimination

The haploidizing male killer hypothesis suggests an evolutionary origin for paternal genome elimination (PGE) that is consistent with the ecological correlates of ancestral haplodiploid insect clades. We make use of population genetics models to test the logic and assumptions of this hypothesis with particular emphasis on the co-evolution between bacteria and host. We derive simple invasion conditions for rare modifiers of bacteria transmission and rare modifiers of host survivorship after haploidization. We also study the evolutionary dynamics of both these modifiers. We conclude that PGE shows evolutionary genetic stability and present a comprehensive analysis of the probability that such genetic system evolves due to the action of cytoplasmic genes.     

Maternal imprints and the origins of variation

The non-genomic transmission of maternal behavior from one generation to the next illustrates the pervasive influence of maternal care on offspring development and the high degree of plasticity within the developing maternal brain. Investigations of the mechanisms through which these maternal effects are achieved have demonstrated environmentally-induced changes in gene expression associated with epigenetic modifications within the promoter region of target genes. These findings raise challenging questions regarding the pathways linking experience to behavioral variation and the broader ecological/evolutionary implications of the dynamic changes in neuroendocrine function that emerge. This review will highlight studies in laboratory rodents which demonstrate plasticity in the maternal brain and the role of maternally-induced changes in DNA methylation in establishing the link between variations in maternal care and consequent developmental outcomes. The persistence of maternal effects across generations and the trade-offs in reproduction that are evident in female offspring who experience high vs. low levels of maternal care contribute to our understanding of the divergent strategies that are triggered by the quality of early-life experiences. Evolving concepts of inheritance and the interplay between genes and the environment may advance our understanding of the origins of individual differences in phenotype.     

Apparent transgenerational effects of host plant in the leaf beetle Ophraella notulata (Coleoptera: Chrysomelidae)

The natural host of Ophraella notulata is Iva frutescens (Asteraceae); its close relative feeds on a related plant, Ambrosia artemisiifolia. We reared beetles on both plants, obtained progeny from the four possible crosses (two sexes X two parental hosts), and reared the progeny on both plant species. Survival to the imaginal stage of progeny reared on Iva varied with both maternal and paternal host. Hatchling feeding response to both plants showed a maternal host X paternal host interaction. Consumption of Ambrosia by adult beetles was, counter to expectation, higher for progeny of Iva-reared males than Ambrosia-reared males. Oviposition response, although based on too few data to be definitive, was peculiar: parental host did not affect oviposition on Ambrosia; on Iva daughters of Iva-reared males laid significantly more eggs than did daughters of Ambrosia-reared males, but only if they had been reared on Iva; those reared on Ambrosia displayed the reverse pattern. We discuss the possibility that nongenetic paternal transmission of host plant effects may explain these results, but offer a somewhat uncomfortable hypothesis of selection as a preferable explanation. An important outcome of the experiment is that it provided no evidence of maternal effects of host plant on offspring feeding or oviposition.     

Perceived mate fidelity and paternal resemblance predict men's investment in children

Here, we investigate whether variation in male parental investment can be explained in terms of (1) men's perception of the degree of resemblance between themselves and their offspring and (2) men's perception of their mates' fidelity. In a sample of men from London's Heathrow airport, both variables were found to predict reported investment. We also examined whether the predictors of investment varied when men were no longer in a relationship with the mother of their children and are therefore no longer investing in mating effort with them. Among men no longer in a relationship with the mother of their children, resemblance became a stronger predictor of investment, while fidelity was no longer a significant predictor. Overall, men provided less investment to their children if they were no longer in a relationship with the mother of their children.     

Epigenetics and atherosclerosis

The contribution of epigenetic mechanisms to cardiovascular diseases remains poorly understood. Hypomethylation of genomic DNA is present in human atherosclerotic lesions and methylation changes also occur at the promoter level of several genes involved in the pathogenesis of atherosclerosis, such as extracellular superoxide dismutase, estrogen receptor-α, endothelial nitric oxide synthase and 15-lipoxygenase. So far, no clear data is available about histone modification marks in atherosclerotic lesions. It remains unclear whether epigenetic changes are causally related to the pathogenetic features, such as clonal proliferation of lesion smooth muscle cells, lipid accumulation and modulation of immune responses in the lesions, or whether they merely represent a consequence of the ongoing pathological process. However, epigenetic changes could at least partly explain poorly understood environmental and dietary effects on atherogenesis and the rapid increases and decreases in the incidence of coronary heart disease observed in various populations. RNAi mechanisms may also contribute to the epigenetic regulation of vascular cells. Therapies directed towards modification of the epigenetic status of vascular cells might provide new tools to control atherosclerosis-related cardiovascular diseases.     

Epigenetics and parental effects

Parental effects are a major source of phenotypic plasticity and may influence offspring phenotype in concert with environmental demands. Studies of “environmental epigenetics” suggest that (1) DNA methylation states are variable and that both demethylation and remethylation occur in post‐mitotic cells, and (2) that remodeling of DNA methylation can occur in response to environmentally driven intracellular signaling pathways. Studies of mother‐offspring interactions in rodents suggest that parental signals influence the DNA methylation, leading to stable changes in gene expression. If parental effects do indeed enhance the “match” between prevailing environmental demands and offspring phenotype, then the potential for variation in environmental conditions over time would suggest a mechanism that requires active maintenance across generations through parental signaling. We suggest that parental regulation of DNA methylation states is thus an ideal candidate mechanism for parental effects on phenotypic variation.     

Effects of neonatal paternal deprivation or early deprivation on anxiety and social behaviors of the adults in mandarin voles

This study examined whether neonatal paternal deprivation (PD: father was removed and pups were raised just by mother) or early deprivation (ED: pups were raised by both parents except separated from not only the dam but also the peers for three hours a day from PND 0 to 13) has long-term effects on anxiety and social behaviors of adult mandarin voles. Newborn mandarin voles of F2 generation were randomly assigned to one of three groups: bi-parental care (PC: pups were raised by both parents), PD and ED. The parental care behaviors of F1 generation were observed at the age of 0, 13 and 21 days (PND 0, 13, 21) of F2 generation of PC and PD groups. Moreover, each mandarin vole of F2 generation received an open field test and a social interaction test on PND 70 and PND 75, respectively. No significant differences of parental behavior were observed between mothers and fathers from PC families, showing typical parental behavior of socially monogamous rodents. In addition, no significant differences of maternal behaviors were found between mothers from PC and PD families, indicating no maternal compensation towards pups for the absence of the paternal care. In the open field test, mandarin voles from both PD and ED families displayed higher levels of anxiety and lower locomotor activity, relative to offspring of PC family. In the social interaction test, both PD and ED mandarin voles also showed lower levels of social behavior and higher levels of anxiety. Thus, both PD and ED significantly increase anxiety and reduce social behavior of adult mandarin voles, suggesting that variation in parental investment may lead to variation in anxiety and social behaviors in rodents with different mating systems.     

Epigenetics in asthma and COPD

Epigenetic mechanisms are likely to play a role in many complex diseases, the extent of which we only beginning to understand. COPD and asthma are two respiratory diseases subject to strong environmental influences depending on underlying genetic susceptibility. Epigenetic mechanisms such as DNA methylation, histone modification and microRNA may be involved in these processes by modulating environmental effects to influence disease development. Given their demonstrated modifiable nature, epigenetic mechanisms may open new possibilities for therapeutic intervention. Here we give an overview of recent developments in the field of respiratory epigenetics in relation to asthma and COPD in the context of our current understanding of mechanisms leading to such diseases.     

Prolactin responses to infant cues in men and women: effects of parental experience and recent infant contact

We used a longitudinal design to test whether parental experience differentially affects the development of prolactin responses to infant cues in men and women. Couples provided two blood samples at three tests, one test just before their babies were born, and two tests during the early postnatal period (n=21). Nine couples repeated the tests near the birth of their second babies. In the 30 min between the two samples, couples listened to recorded infant cries at the prenatal test and held their baby (fathers) or a doll (mothers) at the postnatal tests. Blood samples were analyzed for prolactin concentrations. Prolactin values were then related to sex and parity differences as well as to questionnaire data concerning emotional responses to infant cries and previous infant contact. We found that (1) prior to the birth of both the first and second babies, women's prolactin concentrations increased after exposure to infant stimuli, whereas men's prolactin concentrations decreased; postnatal sex differences varied with parity; (2) women's prolactin reactivity did not change significantly with parental experience; (3) the same men's prolactin concentrations decreased after holding their first newborns but increased after holding their second newborns; this change was not gradual or permanent; (4) men reporting concern after hearing recorded infant cries showed a different postnatal pattern of prolactin change after holding their babies than men not reporting concern; and (5) men who had little contact with their babies just prior to testing had a more positive prolactin response than men who had recently held their babies for longer periods. Although parental experience appears to affect men's prolactin responses, differences in reactivity were also related to patterns of recent infant contact and individual differences in responses to infant cues.     

哺乳类早期亲本缺失对子代行为及神经内分泌的影响

亲本投资作为一种早期社会环境对个体发育产生显著的影响。而某些原因会导致哺乳类亲本缺失,造成亲本投资改变。最近有关亲本缺失对子代的影响有较多的研究,本文主要综述了早期母本剥夺、父本剥夺和早期隔离分别对子代成年后情绪、认知及攻击行为、育幼行为和配偶关系的建立等多种社会行为的影响,并总结了这些早期发育的社会环境对神经内分泌的效应,并指出本领域需要解决的问题,希望有助于正确认识哺乳类不同亲本投资对后代行为的影响及相关神经内分泌机制。以上研究可为哺乳类异常行为的发生机制的理解提供重要线索,也为野生动物和实验动物的科学管理提供重要启示。     

Maternal effects on phase characteristics in the desert locust, Schistocerca gregaria: a review of current understanding

Desert locusts demonstrate pronounced density-dependent polyphenism: a complex suite of traits shifts over the lifetime of an individual in response to crowding or isolation. These changes also accumulate across generations through a maternal effect. Female desert locusts alter the developmental trajectory of their offspring in response to their own experience of crowding. The mother possesses a memory of both the recency and extent of crowding and shifts the phase state of her hatchlings accordingly. Extensive experimental work has shown that offspring behaviour is controlled by a low molecular weight, polar compound (or compounds) released from the mother's accessory glands. The chemical identity of this agent is not yet known.     

Predator-induced maternal and paternal effects independently alter sexual selection

Parental experience alters survival-related phenotypes of offspring in both adaptive and nonadaptive ways, yielding rapid inter- and transgenerational fitness effects. Yet, fitness comprises survival and reproduction, and parental effects on mating decisions could alter the strength and direction of sexual selection, affecting long-term evolutionary trajectories. We used a full factorial design in which threespine stickleback (Gasterosteus aculeatus) mothers, fathers, both, or neither were exposed to a model predator at developmentally appropriate times to test for predator-induced maternal, paternal, and joint parental effects on daughters’ mating behavior. We tested the responsiveness, preferences, and mate choices of adult daughters in no-choice trials with wild-caught males who had varied sexual signals. Maternal and paternal predator exposure independently yielded daughters who preferred males who were intermediate in conspicuousness (with duller nuptial coloration and who courted less vigorously), relaxing the typical preference for the most conspicuous males. The combined effects of maternal and paternal predator exposure were not cumulative; when both parents were predator exposed, single-parent effects on mate preferences were reversed. Thus, we cannot assume that maternal and paternal effects additively combine to produce “parental” effects. Further, joint parental predator exposure yielded daughters who were three times less likely to mate at all. Stress-induced intergenerational parental effects on reproductive decisions such as those observed here may potentiate rapid transgenerational responses to novel and changing mating environments.     

Perceptions of paternal resemblance predict family violence

Fifty-five men participating in a domestic violence treatment program agreed to complete a questionnaire and rate the degree to which their children looked like them. Ratings of paternal resemblance were positively correlated with the self-reported quality of the men's relationships with their children and inversely proportional to the severity of injuries suffered by their spouses. Analogous results were also found for the men's experience with their parents. We suggest that these results reflect men's use of paternal resemblance to assess paternity.     

Long-term and transgenerational effects of cryopreservation on rabbit embryos

The short-term effects of cryopreservation and embryo transfer are well documented (reduced embryo viability, changes in pattern expression), but little is known about their long-term effects. We examined the possibility that embryo vitrification and transfer in rabbit could have an impact on the long-term reproductive physiology of the offspring and whether these phenotypes could be transferred to the progeny. Vitrified rabbit embryos were warmed and transferred to recipient females (F0). The offspring of the F0 generation were the F1 generation (cryopreserved animals). Females from F1 generation offspring were bred to F1 males to generate an F2 generation. In addition, two counterpart groups of noncryopreserved animals were bred and housed simultaneously to F1 and F2 generations (CF1 and CF2, respectively). The reproductive traits studied in all studied groups were litter size (LS), number born alive at birth (BA), and postnatal survival at Day 28 (number of weaned/number born alive expressed as percentage). The reproductive traits were analyzed using Bayesian methodology. Features of the estimated marginal posterior distributions of the differences between F1 and their counterparts (F1 − CF1) and between F2 and their counterparts (F2 − CF2) in reproductive characters found that vitrification and transfer procedures cause a consistent increase in LS and BA between F1 and CF1 females (more than 1.4 kits in LS and more than 1.3 BA) and also between F2 and CF2 females (0.96 kits in LS and 0.94 BA). We concluded that embryo cryopreservation and transfer procedures have long-term effects on derived female reproduction (F1 females) and transgenerational effects on female F1 offspring (F2 females).     

Comparative analysis of male androgen responsiveness to social environment in birds: the effects of mating system and paternal incubation

Male androgen responses to social challenges have been predicted to vary with mating system, male-male aggressiveness, and the degree of paternal investment in birds ("challenge hypothesis," Am. Nat. 136 (1990), 829). This study focused on the interspecific predictions of the challenge hypothesis. Comparative methods were used to control for effects of the phylogenetic relatedness among the sampled species. Male androgen data of 84 bird species were collected from literature records on seasonal androgen patterns. From these, the androgen responsiveness (AR) was calculated as described in the original challenge hypothesis (i.e., maximum physiological level/breeding baseline). Scatterplots of AR versus mating strategy, male-male aggressiveness, and the degree of paternal care confirmed the expected interspecific patterns. When phylogenetic analyses were performed among all of the sampled species, the effects of paternal investment disappeared while the AR remained covarying to a high degree with mating system and male-male aggressiveness. Although these mechanisms may be different at the intraspecific level, this suggests that interspecific differences of AR in male birds may have evolved in response to changes of mating strategies, rather than in response to altered paternal duties. However, control for phylogeny among the subsample of 32 passerine species revealed that if any paternal investment contributed to the observed variance in AR, then the change from "no male incubation" to "male shares incubation duties" represented the most effective, whereas the male's contribution to feeding offspring did not explain the observed variation of AR.     

表观遗传学研究方法进展

表观遗传调控是基因表达调控的重要组成部分,已成为当前研究的热点.目前其研究主要集中在DNA甲基化和组蛋白修饰.针对这两种表观修饰,其研究方法也取得了较太进展,一方面方法的是敏度和特异性都在不断提高;另一方面表现修饰的检测正在逐步从定性检测向定量分析方向发展,从个别位点向高通量检测发展.此外,新一代测序技术的应用特大大推动表观遗传研究的发展,包括单分子实时测序法、单分子纳米孔科序法等.综述目前常用的DNA甲基化、组蛋白修饰研究方法以及最新的单分子测序技术,并对它们在表观遗传修饰检测中的应用作了简要对比分析.     

Paternal Care by Genetic Fathers and Stepfathers I: Reports from Albuquerque Men

We present a biosocial model of human male parental care that allows male parental allocations to be influenced not only by changes in the fitness (welfare) of the recipient offspring, but also by their effects on the man's relationship with the child's mother. The model recognizes four classes of relationships between males and the children they parent: genetic offspring of current mates (combined relationship and parental effort), genetic offspring of previous mates (parental effort solely), step offspring of current mates (relationship effort solely), and stepchildren of previous mates (essentially no expected investment). We test the model using data on parental investments collected from adult males living in Albuquerque, New Mexico, U.S.A. Four measures of paternal investment are examined: the probability that a child attends college (2,191 offspring), the probability that a child who attends college receives money for it (N = 1,212), current financial expenditures on children (N = 635), and the amount of time per week that men spend with children ages 5 to 12 years (N = 2,589). The tests are consistent with a role for relationship effort in parental care: men invest more in the children of their current mates, even when coresidence with offspring is not a confounder.     

Interaction between maternal effects and temperature affects diapause occurrence in the cricket Allonemobius socius

The induction of diapause can be adaptive for egg survival during unfavorable conditions, while direct development can be advantageous under favorable conditions by allowing additional generations to exploit abundant resources. Therefore, the physiological capability of a female to respond to environmental cues indicative of habitat quality by producing eggs of the appropriate developmental phenotype should be under strong selection. Additionally, developing embryos may alter the developmental trajectory initiated by the female in response to changing environmental conditions. In this study, we used a cross-fostering approach to isolate the maternal effects of parental diapause history (not previously studied) and egg-laying temperature from the influence of the incubation environment experienced by the developing embryo on the proportion of diapause eggs produced by the striped ground cricket, Allonemobius socius. We found that an interaction between egg-incubation temperature and parental diapause history strongly affected the proportion of diapause eggs produced and the proportion of eggs that hatched within a 16–18 day incubation period, while egg-laying temperature and all other interactions did not. These novel results indicate that embryos can respond directly to the environmental conditions they experience during development, but that their ability to do so is influenced by maternal effects such as parental diapause history. The results of this study not only provide evidence, for the first time, of parental diapause history affecting diapause proportions, but also raise additional questions about the mechanism by which environmental information is transmitted from parent to offspring and how offspring are able to respond to conditions experienced during their own development.     

Independent origins of Indian caste and tribal paternal lineages

The origins of the nearly one billion people inhabiting the Indian subcontinent and following the customs of the Hindu caste system are controversial: are they largely derived from Indian local populations (i.e. tribal groups) or from recent immigrants to India? Archaeological and linguistic evidence support the latter hypothesis, whereas recent genetic data seem to favor the former hypothesis. Here, we analyze the most extensive dataset of Indian caste and tribal Y chromosomes to date. We find that caste and tribal groups differ significantly in their haplogroup frequency distributions; caste groups are homogeneous for Y chromosome variation and more closely related to each other and to central Asian groups than to Indian tribal or any other Eurasian groups. We conclude that paternal lineages of Indian caste groups are primarily descended from Indo-European speakers who migrated from central Asia approximately 3,500 years ago. Conversely, paternal lineages of tribal groups are predominantly derived from the original Indian gene pool. We also provide evidence for bidirectional male gene flow between caste and tribal groups. In comparison, caste and tribal groups are homogeneous with respect to mitochondrial DNA variation, which may reflect the sociocultural characteristics of the Indian caste society.