The sperm epigenome and potential implications for the developing embryo (original) (raw)
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Systems Biology in Reproductive Medicine, 2017
The mammalian sperm contains a highly unique and specialized epigenetic landscape that offers a great degree of interesting research opportunities. One key discriminating feature of the mature sperm epigenome is that it, in theory, represents both remnant marks used throughout spermatogenesis to generate sperm cells competent to perform their function, but also marks that appear to be useful beyond fertilization. Key questions must be asked about the utility of these marks and the multiple purposes that may be served. It is this unique epigenetic landscape that has driven some labs to begin to study the links between aberrant sperm epigenetic patterns and various forms of infertility, from idiopathic to alterations in sperm motility, morphology, and viability and fertilization capacity. Because of the unique nature of the sperm epigenome and the patterns found in mature sperm that appear to reflect perturbations in spermatogenesis that may ultimately have effect on pregnancy outcomes, some researchers believe that these marks may provide predictive insight that can be exploited. Indeed, there is emerging data suggesting that the predictive power of DNA methylation and RNA signatures in sperm likely exceeds that which can be found with traditional assessments of male infertility. This review will focus on the utilization of the sperm epigenome as a potential diagnostic tool in the context of male infertility, as well as the potential difficulties associated with such an approach.
Sperm nuclear proteome and its epigenetic potential
Andrology, 2014
The main function of the sperm cell is to transmit the paternal genetic message and epigenetic information to the embryo. Importantly, the majority of the genes in the sperm chromatin are highly condensed by protamines, whereas genes potentially needed in the initial stages of development are associated with histones, representing a form of epigenetic marking. However, so far little attention has been devoted to other sperm chromatin-associated proteins that, in addition to histones and protamines, may also have an epigenetic role. Therefore, with the goal of contributing to cover this subject we have compiled, reviewed and report a list of 581 chromatin or nuclear proteins described in the human sperm cell. Furthermore, we have analysed their Gene Ontology Biological Process enriched terms and have grouped them into different functional categories. Remarkably, we show that 56% of the sperm nuclear proteins have a potential epigenetic activity, being involved in at least one of the ...
On the origin of sperm epigenetic heterogeneity
Reproduction (Cambridge, England), 2016
The influence of epigenetic modifications on reproduction and on the function of male germ cells has been thoroughly demonstrated. In particular, aberrant DNA methylation levels in sperm have been associated with abnormal sperm parameters, lower fertilization rates and impaired embryo development. Recent reports have indicated that human sperm might be epigenetically heterogeneous and that abnormal DNA methylation levels found in sperm of infertile men could be due to the presence of sperm populations with different epigenetic quality. However, the origin and the contribution of different germ cell types to this suspected heterogeneity remain unclear. In this review we focus on sperm epigenetics at the DNA methylation level and its importance for reproduction. We take into account the latest developments and hypotheses concerning the functional significance of epigenetic heterogeneity coming from the field of stem cell and cancer biology and discuss the potential importance and cons...
Epigenetics and its role in male infertility
Journal of Assisted Reproduction and Genetics, 2012
Male infertility is a common and complex problem affecting 1 in 20 men. Despite voluminous research in this field, in many cases, the underlying causes are unknown. Epigenetic factors play an important role in male infertility and these have been studied extensively. Epigenetic modifications control a number of processes within the body, but this review will concentrate on male fertility and the consequences of aberrant epigenetic regulation/modification. Many recent studies have identified altered epigenetic profiles in sperm from men with oligozoospermia and oligoasthenoteratozoospermia. During gametogenesis and germ cell maturation, germ cells undergo extensive epigenetic reprogramming that involves the establishment of sex-specific patterns in the sperm and oocytes. Increasing evidence suggests that genetic and environmental factors can have negative effects on epigenetic processes controlling implantation, placentation and fetal growth. This review provides an overview of the epigenetic processes (histone-to-protamine exchange and epigenetic reprogramming post-fertilization), aberrant epigenetic reprogramming and its association with fertility, possible risks for ART techniques, testicular cancer and the effect of environmental factors on the epigenetic processes.
Understanding the Epigenetic Modifications in Sperm Genome
Sperm genome condensation is mainly important as the genome expression should be repressed until it is fertilised with oocyte. In most of the mammals, protamines play an important role in genome condensation. In humans, histone variants were present in germ cells when compared with somatic cells. How successful replacement of histones by protamines occurs in most of the mammals is an interesting question. Little information is known about transition proteins that replace histones with protamines. Apart from condensation, which mechanisms prevent expression of X and Y chromosomes in sperm is to be studied. If exposed to genotoxic agents like Metosartan that damage testes should also be considered, in order for assisted reproductive technologies like in vitro fertilisation to succeed.
Epigenetics in Male Infertility
Male Reproductive Anatomy [Working Title], 2021
Male infertility is a complex medical condition, in which epigenetic factors play an important role. Epigenetics has recently gained significant scientific attention since it has added a new dimension to genomic and proteomic research. As a mechanism for maintaining genomic integrity and controlling gene expression, epigenetic modifications hold a great promise in capturing the subtle, yet very important, regulatory elements that might drive normal and abnormal sperm functions. The sperm’s epigenome is known to be marked by constant changing over spermatogenesis, which is highly susceptible to be influenced by a wide spectrum of environmental stimuli. Recently, epigenetic aberrations have been recognized as one of the causes of idiopathic male infertility. Recent advances in technology have enabled humans to study epigenetics role in male infertility.
Epigenetic regulation in male germ cells
Reproduction, 2008
In recent years, it has become increasingly clear that epigenetic regulation of gene expression is critical during spermatogenesis. In this review, the epigenetic regulation and the consequences of its aberrant regulation during mitosis, meiosis and spermiogenesis are described. The current knowledge on epigenetic modifications that occur during male meiosis is discussed, with special attention on events that define meiotic sex chromosome inactivation. Finally, the recent studies focused on transgenerational and paternal effects in mice and humans are discussed. In many cases, these epigenetic effects resulted in impaired fertility and potentially long-ranging affects underlining the importance of research in this area.
Epigenetic disorders and male subfertility
Fertility and Sterility, 2013
Objective: To provide a link between epigenetics and male subfertility at the DNA, histone-protamine, and RNA levels and its consequences on fertilization and embryo development. Design: Review of the relevant literature. Setting: University-based clinical and research laboratories. Patient(s): Fertile and infertile men. Intervention(s): None. Main Outcome Measure(s): Critical review of the literature. Result(s): Epigenetic markers can be modified in infertile patients. Epigenetic modifications include methylation loss or gain on the global level and on imprinted genes, high levels of histone retention in spermatozoa, and deficiencies in some transcripts involved in spermatogenesis. Interestingly, these abnormalities are all linked together, because DNA methylation maintenance depends on DNA histone-protamine configuration which itself is stabilized by spermatozoal RNAs. Conclusion(s): The paternal genome has long been considered to be silent and passive in embryo formation. The epigenetic processes associated with the paternal DNA genome highlights its importance in male fertility as well as for embryo development. (Fertil Steril Ò 2013;99: 624-31. Ó2013 by American Society for Reproductive Medicine.
PLoS ONE, 2007
Background. Male-factor infertility is a common condition, and etiology is unknown for a high proportion of cases. Abnormal epigenetic programming of the germline is proposed as a possible mechanism compromising spermatogenesis of some men currently diagnosed with idiopathic infertility. During germ cell maturation and gametogenesis, cells of the germ line undergo extensive epigenetic reprogramming. This process involves widespread erasure of somatic-like patterns of DNA methylation followed by establishment of sex-specific patterns by de novo DNA methylation. Incomplete reprogramming of the male germ line could, in theory, result in both altered sperm DNA methylation and compromised spermatogenesis. Methodology/ Principal Finding. We determined concentration, motility and morphology of sperm in semen samples collected by male members of couples attending an infertility clinic. Using MethyLight and Illumina assays we measured methylation of DNA isolated from purified sperm from the same samples. Methylation at numerous sequences was elevated in DNA from poor quality sperm. Conclusions. This is the first report of a broad epigenetic defect associated with abnormal semen parameters. Our results suggest that the underlying mechanism for these epigenetic changes may be improper erasure of DNA methylation during epigenetic reprogramming of the male germ line.