Genetic and epigenetic effects on centromere establishment

Chromosoma - Endogenous chromosomes contain centromeres to direct equal chromosomal segregation in mitosis and meiosis. The location and function of existing centromeres is usually maintained...     

Genetic and epigenetic effects of environmental arsenicals

Environmental arsenic compounds and their methylated metabolites do not form adducts with DNA, but do cause oxidative DNA damage. Chromosome aberrations are seen at toxic concentrations. Genetic effects that occur at non-toxic concentrations include aneuploidy, comutagenesis (resulting from indirect effects on DNA repair), and delayed mutagenesis (probably secondary to aneuploidy and/or epigenetic effects). Effects of trivalent arsenicals on poly(ADP ribose) polymerase and P53 activation may mediate effects on DNA repair and aneuploidy. A growing literature points to the epigenetic effects of arsenic compounds in cells and in vivo. A review of the current literature on DNA methylation, histone modifications and microRNA effects is presented.     

Genetic and epigenetic effects of salinity on in vitro growth of barley

Morphological, physiological and molecular changes were investigated in in vitro salt-stressed barley (Hordeum vulgare L. cv. Tokak). Mature embryos were cultured in Murashige and Skoog medium containing 0 (control), 50 and 100 mM NaCl for 20 days. Both concentrations inhibited shoot growth, decreased fresh weight and protein content, and increased SOD (EC 1.15.1.1) activity in a dose-dependent manner. The lower concentration increased root growth. Salinity caused nucleotide variations in roots, but did not affect shoot DNAs. The higher concentration caused methylation changes, mainly hypermethylation in shoots. This is the first study on genetic and epigenetic effects of salinity in barley.     

Hierarchical phenotypic and epigenetic variation in cloned swine

Cloning by somatic cell nuclear transfer can result in the birth of animals with phenotypic and gene expression abnormalities. We compared adult cloned pigs and adult pigs from naturally bred control females using a series of physiological and genetic parameters, including detailed methylation profiles of selected genomic regions. Phenotypic and genetic analyses indicated that there are two classes of traits, one in which the cloned pigs have less variation than controls and another characterized by variation that is equally high in cloned and control pigs. Although cloning creates animals within the normal phenotypic range, it increases the variability associated with some traits. This finding is contrary to the expectation that cloning can be used to reduce the size of groups involved in animal experimentation and to reproduce an animal, including a pet, with a homogenous set of desired traits.     

Short-term variation in sperm competition causes sperm-mediated epigenetic effects on early offspring performance in the zebrafish

The inheritance of non-genetic factors is increasingly seen to play a major role in ecology and evolution. While the causes and consequences of epigenetic effects transmitted from the mother to the offspring have received ample attention, much less is known about how variation in the condition of the father affects the offspring. Here, we manipulated the intensity of sperm competition experienced by male zebrafish Danio rerio to investigate the potential for sperm-mediated epigenetic effects over a relatively short period of time. We found that the rapid responses of males to varying intensity of sperm competition not only affected sperm traits as shown previously, but also the performance of the resulting offspring. We observed that males exposed to high intensity of sperm competition produced faster swimming and more motile sperm, and sired offspring that hatched over a narrower time frame but exhibited a lower survival rate than males exposed to low intensity of sperm competition. Our results provide striking evidence for short-term paternal effects and the possible fitness consequences of such sperm-mediated non-genetic factors not only for the resulting offspring but also for the female.     

Genetic and epigenetic regulators of pluripotency

Genetic and epigenetic mechanisms regulate the transition from the totipotent zygote to pluripotent primitive ectoderm cells in the inner cell mass of mouse blastocysts. These pluripotent cells can be propagated indefinitely in vitro, underpinned by a unique epigenetic state. Following implantation of the blastocyst, diverse epigenetic modifiers control differentiation of pluripotent epiblast cells into somatic cells, while specification of germ cells requires repression of the somatic program. Regenerating totipotency during development of germ cells entails re-expression of pluripotency-specific genes and extensive erasure of epigenetic modifications. Increasing knowledge of key underlying mechanisms heightens prospects for creating pluripotent cells directly from adult somatic cells.     

Genetic and epigenetic markers of gliomas

Malignant gliomas are aggressive and highly invasive tumors. Various genetic and epigenetic changes are common for these tumors. Mostly they concern the genes involved in cell-cycle regulation, apoptotic pathways, cell invasion, angiogenesis, and cell metabolism. The role of epigenetic mechanisms in glioma malignant transformation, despite recent progress, is uncertain and remains under intense study. This review describes the mechanisms of epigenetic regulation of gene expression, including posttranslational modifications of histones, DNA methylation in promoter regions, and microRNA regulation. The genetic and epigenetic factors driving the pathogenesis of gliomas in their possible mutual influence and the potential epigenetic targets that can be used for diagnostics and new therapeutic approaches are also discussed.     

The epigenetic basis of gender in flowering plants and mammals

What makes a sperm male or an egg female, and how can we tell? A gamete's gender could be defined in many ways, such as the sex of the individual or organ that produced it, its cellular morphology, or its behaviour at fertilization. In flowering plants and mammals, however, there is an extra dimension to the gender of a gamete – due to parental imprinting, some of the genes it contributes to the next generation will have different expression patterns depending on whether they were maternally or paternally transmitted. The non-equivalence of gamete genomes, along with natural and experimental modification of imprinting, reveal a level of sexual identity that we describe as ‘epigender’. In this paper, we explore epigender in the life history of plants and animals, and its significance for reproduction and development.     

The health of somatic cell cloned cattle and their offspring

The cloning syndrome is a continuum with the consequences of abnormal reprogramming manifest throughout gestation, the neo-natal period, and into adulthood in the cloned generation, but it does not appear to be transmitted to subsequent offspring following sexual reproduction. Most in vivo studies on bovine somatic cell cloning have focused on development during pregnancy and the neo-natal period. In this paper, we report on the viability and health of cloned cattle in adulthood. From our studies at AgResearch, we find that between weaning and 4 years of age, the annual mortality rate in cattle cloned from somatic cells is at least 8%. Although the reasons for death are variable and some potentially preventable, the main mortality factor in this period is euthanasia due to musculoskeletal abnormalities. This includes animals with severely contracted flexor tendons and those displaying chronic lameness, particularly in milking cows. In contrast, no deaths beyond weaning have so far been encountered with the offspring of clones where the oldest animals are 3 years of age. In surviving cloned cattle, blood profiles and other indicators of general physiological function such as growth rate, reproduction, rearing of offspring, and milk production are all within the normal phenotypic ranges.     

Zootechnical performance of cloned cattle and offspring: preliminary results

This paper presents information on the evolution of sets of cloned heifers of Holstein breed in comparison to that of control heifers derived from artificial insemination (AI) in the same farm, as well as data on a set of cloned bulls and their semen characteristics. Preliminary observations on a group of calves sired by a cloned bull and offspring of cloned females are reported. Mean birth weight in the clone group (50 females) was statistically higher than that of 68 contemporary female controls obtained by AI (49.27 +/- 10.98 vs. 40.57 +/- 5.55 kg, respectively, p < 0.05). Growth rate was within normal values for Holstein heifers (from 0.7 to 0.8 kg/day) and daily gain was not influenced by the high or low birth weight of clones. Within animals of the same clone, variability of daily gain was reduced compared to their control counterparts. Semen production from three cloned bulls was within the parameters expected for young bull of the same age. A direct comparison of morphological analysis was made between the frozen thawed semen of the donor bull and of his three clones collected at the same age. The overall semen picture appeared within acceptable limits and the clones presented similar percentages of sperm abnormalities (80% of morphologically normal spermatozoa) as the donor. These preliminary results suggest no deleterious effect of cloning on the semen picture of cloned sires. Frozen semen from one clone bull was used for an AI trial, resulting in 65% pregnancies, 25 live calves were naturally delivered. Concerning the offspring of both female and male clones, the phenotypical and clinical observation of the calves in the first week of age did not reveal any clinical abnormality, suggesting that the deviations observed in clones are not transmitted to the progeny.     

Sex differences in sand lizard telomere inheritance: paternal epigenetic effects increases telomere heritability and offspring survival

Background

To date, the only estimate of the heritability of telomere length in wild populations comes from humans. Thus, there is a need for analysis of natural populations with respect to how telomeres evolve.

Methodology/Principal Findings

Here, we show that telomere length is heritable in free-ranging sand lizards, Lacerta agilis. More importantly, heritability estimates analysed within, and contrasted between, the sexes are markedly different; son-sire heritability is much higher relative to daughter-dam heritability. We assess the effect of paternal age on Telomere Length (TL) and show that in this species, paternal age at conception is the best predictor of TL in sons. Neither paternal age per se at blood sampling for telomere screening, nor corresponding age in sons impact TL in sons. Processes maintaining telomere length are also associated with negative fitness effects, most notably by increasing the risk of cancer and show variation across different categories of individuals (e.g. males vs. females). We therefore tested whether TL influences offspring survival in their first year of life. Indeed such effects were present and independent of sex-biased offspring mortality and offspring malformations.

Conclusions/Significance

TL show differences in sex-specific heritability with implications for differences between the sexes with respect to ongoing telomere selection. Paternal age influences the length of telomeres in sons and longer telomeres enhance offspring survival.     

An epigenetic aberration increased in intergenic regions of cloned mice

The causes of frequent abnormal phenotypes and low success rate in mammalian cloning are poorly understood. Although epigenetic aberration is suspected to be a cause, its connection to the phenotypes has yet to be investigated. To measure the level of reprogramming of an epigenetic mark, acetylation at lysine 9 of histone H3 (H3K9Ac), in cloned mice, we examined its conservation between two cloned mice derived from distinct cell nuclei and their natural donors by utilizing whole-genome tiling arrays and quantitative PCR. Pairwise comparison of the H3K9Ac enrichment profile between the four mice revealed that H3K9Ac is less conserved in intergenic regions than in promoter regions of protein-coding genes. Intriguingly, the variation of H3K9Ac enrichment in intergenic regions is the most prominent in comparison of the two clones, possibly reflecting an additive effect of aberrant reprogramming of this epigenetic information occurring specifically in each of the two clones.     

Hormonally mediated maternal effects shape offspring survival potential in stressful environments

In most egg-laying vertebrates, maternal responses to stressful conditions are translated into the release of glucocorticoid hormones such as cortisol, which are then transmitted to their developing embryos. Although such maternally transmitted hormonal resources have been shown to influence or even interfere with the optimal developmental trajectories of offspring in many taxa, their influence on the dynamics of wild fish populations remains largely unexplored. Here, we examined the extent to which simulated hormonally mediated maternal effects influence the development and early survival of the coral reef damselfish, Pomacentrus amboinensis. Concentrations of cortisol in the eggs were manipulated within naturally occurring limits by immersion. We found that the proportion of embryos that delayed hatching when exposed to high levels of cortisol was considerably lower than in the other two treatments (low cortisol dose and control). High cortisol levels in P. amboinensis eggs resulted in increased egg mortality and greater asymmetry in hatchlings. For embryos that successfully hatched, individuals from the elevated cortisol treatments (especially low dose) survived longer after hatching. Although individuals that originated from eggs with elevated cortisol levels survived longer after hatching, they may not gain an overall survival advantage. Our results suggest that subtle increases in the allocation of maternally derived hormones, such as cortisol, to offspring are a direct way for stressed mothers to endow their young with an immediate survival advantage. We propose that this immediate benefit outweighs the developmental costs which may be expressed as reduced fitness at later life stages. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.