RESUMO
In adult mammals, many heart muscle cells (cardiomyocytes) are polyploid, do not proliferate (post-mitotic), and, consequently, cannot contribute to heart regeneration. In contrast, fetal and neonatal heart muscle cells are diploid, proliferate, and contribute to heart regeneration. We have identified interdependent changes of the nuclear lamina, nuclear pore complexes, and DNA-content (ploidy) in heart muscle cell maturation. These results offer new perspectives on how cells alter their nuclear transport and, with that, their gene regulation in response to extracellular signals. We present how changes of the nuclear lamina alter nuclear pore complexes in heart muscle cells. The consequences of these changes for cellular regeneration and stress response in the heart are discussed.
Assuntos
Lâmina Nuclear , Poro Nuclear , Animais , Ploidias , Diferenciação Celular , Laminas , MamíferosRESUMO
Background and Objectives: The human genome contains â¼20,000 genes, each of which has its own set of complex regulatory systems to govern precise expression in each developmental stage and cell type. Here, we report a female patient with congenital weakness, respiratory failure, skeletal dysplasia, contractures, short stature, intellectual delay, respiratory failure, and amenorrhea who presented to Medical Genetics service with no known cause for her condition. Methods: Whole-exome and whole-genome sequencing were conducted, as well as investigational functional studies to assess the effect of SOX8 variant. Results: The patient was found to have biallelic SOX8 variants (NM_014587.3:c.422+5G>C; c.583dup p.(His195ProfsTer11)). SOX8 is a transcriptional regulator, which is predicted to be imprinted (expressed from only one parental allele), but this has not yet been confirmed. We provide evidence that while SOX8 was maternally expressed in adult-derived fibroblasts and lymphoblasts, it was biallelically expressed in other cell types and therefore suggest that biallelic variants are associated with this recessive condition. Functionally, we showed that the paternal variant had the capacity to affect mRNA splicing while the maternal variant resulted in low levels of a truncated protein, which showed decreased binding at and altered expression of SOX8 targets. Discussion: Our findings associate SOX8 variants with this novel condition, highlight how complex genome regulation can complicate novel disease-gene identification, and provide insight into the molecular pathogenesis of this disease.
RESUMO
Genomic imprinting is a parent-of-origin dependent phenomenon that restricts transcription to predominantly one parental allele. Since the discovery of the first long noncoding RNA (lncRNA), which notably was an imprinted lncRNA, a body of knowledge has demonstrated pivotal roles for imprinted lncRNAs in regulating parental-specific expression of neighboring imprinted genes. In this Review, we will discuss the multiple functionalities attributed to lncRNAs and how they regulate imprinted gene expression. We also raise unresolved questions about imprinted lncRNA function, which may lead to new avenues of investigation. This Review is dedicated to the memory of Denise Barlow, a giant in the field of genomic imprinting and functional lncRNAs. With her passion for understanding the inner workings of science, her indominable spirit and her consummate curiosity, Denise blazed a path of scientific investigation that made many seminal contributions to genomic imprinting and the wider field of epigenetic regulation, in addition to inspiring future generations of scientists.
Assuntos
Impressão Genômica , RNA Longo não Codificante/genética , Animais , Humanos , RNA Longo não Codificante/metabolismoRESUMO
BACKGROUND: Over the last several decades, the average age of first-time mothers has risen steadily. With increasing maternal age comes a decrease in fertility, which in turn has led to an increase in the use of assisted reproductive technologies by these women. Assisted reproductive technologies (ARTs), including superovulation and embryo culture, have been shown separately to alter imprinted DNA methylation maintenance in blastocysts. However, there has been little investigation on the effects of advanced maternal age, with or without ARTs, on genomic imprinting. We hypothesized that ARTs and advanced maternal age, separately and together, alter imprinted methylation in mouse preimplantation embryos. For this study, we examined imprinted methylation at three genes, Snrpn, Kcnq1ot1, and H19, which in humans are linked to ART-associated methylation errors that lead to imprinting disorders. RESULTS: Our data showed that imprinted methylation acquisition in oocytes was unaffected by increasing maternal age. Furthermore, imprinted methylation was normally acquired when advanced maternal age was combined with superovulation. Analysis of blastocyst-stage embryos revealed that imprinted methylation maintenance was also not affected by increasing maternal age. In a comparison of ARTs, we observed that the frequency of blastocysts with imprinted methylation loss was similar between the superovulation only and the embryo culture only groups, while the combination of superovulation and embryo culture resulted in a higher frequency of mouse blastocysts with maternal imprinted methylation perturbations than superovulation alone. Finally, the combination of increasing maternal age with ARTs had no additional effect on the frequency of imprinted methylation errors. CONCLUSION: Collectively, increasing maternal age with or without superovulation had no effect of imprinted methylation acquisition at Snrpn, Kcnq1ot1, and H19 in oocytes. Furthermore, during preimplantation development, while ARTs generated perturbations in imprinted methylation maintenance in blastocysts, advanced maternal age did not increase the burden of imprinted methylation errors at Snrpn, Kcnq1ot1, and H19 when combined with ARTs. These results provide cautious optimism that advanced maternal age is not a contributing factor to imprinted methylation errors in embryos produced in the clinic. Furthermore, our data on the effects of ARTs strengthen the need to advance clinical methods to reduce imprinted methylation errors in in vitro-produced embryos.
Assuntos
Envelhecimento/genética , Metilação de DNA , Impressão Genômica , Técnicas de Reprodução Assistida/efeitos adversos , Animais , Blastocisto , Feminino , Humanos , Idade Materna , Camundongos , Modelos Animais , RNA Longo não Codificante/genética , Proteínas Centrais de snRNP/genéticaRESUMO
Genomic imprinting is a phenomenon that restricts transcription to predominantly one parental allele. How this transcriptional duality is regulated is poorly understood. Here we perform an RNA interference screen for epigenetic factors involved in paternal allelic silencing at the Kcnq1ot1 imprinted domain in mouse extraembryonic endoderm stem cells. Multiple factors are identified, including nucleoporin 107 (NUP107). To determine NUP107's role and specificity in Kcnq1ot1 imprinted domain regulation, we deplete Nup107, as well as Nup62, Nup98/96 and Nup153. Nup107, Nup62 and Nup153, but not Nup98/96 depletion, reduce Kcnq1ot1 noncoding RNA volume, displace the Kcnq1ot1 domain from the nuclear periphery, reactivate a subset of normally silent paternal alleles in the domain, alter histone modifications with concomitant changes in KMT2A, EZH2 and EHMT2 occupancy, as well as reduce cohesin interactions at the Kcnq1ot1 imprinting control region. Our results establish an important role for specific nucleoporins in mediating Kcnq1ot1 imprinted domain regulation.
Assuntos
Endoderma/metabolismo , Impressão Genômica , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , RNA Longo não Codificante/genética , Células-Tronco/metabolismo , Animais , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Cruzamentos Genéticos , Embrião de Mamíferos , Endoderma/citologia , Endoderma/crescimento & desenvolvimento , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Histonas/genética , Histonas/metabolismo , Masculino , Camundongos , Proteína de Leucina Linfoide-Mieloide/genética , Proteína de Leucina Linfoide-Mieloide/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Canais de Potássio de Abertura Dependente da Tensão da Membrana/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Longo não Codificante/metabolismo , Células-Tronco/citologia , CoesinasRESUMO
Betaine (N,N,N-trimethylglycine) plays key roles in mouse eggs and preimplantation embryos first in a novel mechanism of cell volume regulation and second as a major methyl donor in blastocysts, but its origin is unknown. Here, we determined that endogenous betaine was present at low levels in germinal vesicle (GV) stage mouse oocytes before ovulation and reached high levels in the mature, ovulated egg. However, no betaine transport into oocytes was detected during meiotic maturation. Because betaine can be synthesized in mammalian cells via choline dehydrogenase (CHDH; EC 1.1.99.1), we assessed whether this enzyme was expressed and active. Chdh transcripts and CHDH protein were expressed in oocytes. No CHDH enzyme activity was detected in GV oocyte lysate, but CHDH became highly active during oocyte meiotic maturation. It was again inactive after fertilization. We then determined whether oocytes synthesized betaine and whether CHDH was required. Isolated maturing oocytes autonomously synthesized betaine in vitro in the presence of choline, whereas this failed to occur in Chdh-/- oocytes, directly demonstrating a requirement for CHDH for betaine accumulation in oocytes. Overall, betaine accumulation is a previously unsuspected physiological process during mouse oocyte meiotic maturation whose underlying mechanism is the transient activation of CHDH.
Assuntos
Betaína/metabolismo , Colina Desidrogenase/metabolismo , Oócitos/enzimologia , Oogênese , Regulação para Cima , Absorção Fisiológica , Animais , Blastocisto/citologia , Blastocisto/enzimologia , Blastocisto/metabolismo , Colina Desidrogenase/química , Colina Desidrogenase/genética , Cruzamentos Genéticos , Ativação Enzimática , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Maturação in Vitro de Oócitos , Meiose , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Mórula/citologia , Mórula/enzimologia , Mórula/metabolismo , Oócitos/citologia , Oócitos/metabolismo , Trítio , Zigoto/citologia , Zigoto/enzimologia , Zigoto/metabolismoRESUMO
Assisted reproductive technologies are fertility treatments used by subfertile couples to conceive their biological child. Although generally considered safe, these pregnancies have been linked to genomic imprinting disorders, including Beckwith-Wiedemann and Silver-Russell Syndromes. Silver-Russell Syndrome is a growth disorder characterized by pre- and post-natal growth retardation. The Mest imprinted domain is one candidate region on chromosome 7 implicated in Silver-Russell Syndrome. We have previously shown that maintenance of imprinted methylation was disrupted by superovulation or embryo culture during pre-implantation mouse development. For superovulation, this disruption did not originate in oogenesis as a methylation acquisition defect. However, in comparison to other genes, Mest exhibits late methylation acquisition kinetics, possibly making Mest more vulnerable to perturbation by environmental insult. In this study, we present a comprehensive evaluation of the effects of superovulation and in vitro culture on genomic imprinting at the Mest gene. Superovulation resulted in disruption of imprinted methylation at the maternal Mest allele in blastocysts with an equal frequency of embryos having methylation errors following low or high hormone treatment. This disruption was not due to a failure of imprinted methylation acquisition at Mest in oocytes. For cultured embryos, both the Fast and Slow culture groups experienced a significant loss of maternal Mest methylation compared to in vivo-derived controls. This loss of methylation was independent of development rates in culture. These results indicate that Mest is more susceptible to imprinted methylation maintenance errors compared to other imprinted genes.
RESUMO
Repetitive genomic regions include tandem sequence repeats and interspersed repeats, such as endogenous retroviruses and LINE-1 elements. Repressive heterochromatin domains silence expression of these sequences through mechanisms that remain poorly understood. Here, we present evidence that the retinoblastoma protein (pRB) utilizes a cell-cycle-independent interaction with E2F1 to recruit enhancer of zeste homolog 2 (EZH2) to diverse repeat sequences. These include simple repeats, satellites, LINEs, and endogenous retroviruses as well as transposon fragments. We generated a mutant mouse strain carrying an F832A mutation in Rb1 that is defective for recruitment to repetitive sequences. Loss of pRB-EZH2 complexes from repeats disperses H3K27me3 from these genomic locations and permits repeat expression. Consistent with maintenance of H3K27me3 at the Hox clusters, these mice are developmentally normal. However, susceptibility to lymphoma suggests that pRB-EZH2 recruitment to repetitive elements may be cancer relevant.
Assuntos
Fator de Transcrição E2F1/genética , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Inativação Gênica , Linfoma/genética , Sequências Repetitivas de Ácido Nucleico , Proteína do Retinoblastoma/genética , Animais , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/mortalidade , Carcinoma Hepatocelular/patologia , Fator de Transcrição E2F1/metabolismo , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Fibroblastos/citologia , Fibroblastos/metabolismo , Predisposição Genética para Doença , Histonas/genética , Histonas/metabolismo , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/mortalidade , Neoplasias Hepáticas/patologia , Linfoma/metabolismo , Linfoma/mortalidade , Linfoma/patologia , Mesentério/metabolismo , Mesentério/patologia , Camundongos , Mutação , Cultura Primária de Células , Ligação Proteica , Proteína do Retinoblastoma/metabolismo , Neoplasias Esplênicas/genética , Neoplasias Esplênicas/metabolismo , Neoplasias Esplênicas/mortalidade , Neoplasias Esplênicas/patologia , Análise de SobrevidaRESUMO
In mice, assisted reproductive technologies (ARTs) applied during gametogenesis and preimplantation development can result in disruption of genomic imprinting. In humans, these technologies and/or subfertility have been linked to perturbations in genomic imprinting. To understand how ARTs and infertility affect DNA methylation, it is important to understand DNA methylation dynamics and the role of regulatory factors at these critical stages. Recent genome studies performed using mouse and human gametes and preimplantation embryos have shed light onto these processes. Here, we comprehensively review the current state of knowledge regarding global and imprinted DNA methylation programming in the mouse and human. Available data highlight striking similarities in mouse and human DNA methylation dynamics during gamete and preimplantation development. Just as fascinating, these studies have revealed sex-, gene-, and allele-specific differences in DNA methylation programming, warranting future investigation to untangle the complex regulation of DNA methylation dynamics during gamete and preimplantation development.
Assuntos
Blastocisto/metabolismo , Metilação de DNA , Desenvolvimento Embrionário/fisiologia , Impressão Genômica , Animais , Feminino , Humanos , Camundongos , Técnicas de Reprodução AssistidaRESUMO
Recently, many advancements in genome-wide chromatin topology and nuclear architecture have unveiled the complex and hidden world of the nucleus, where chromatin is organized into discrete neighbourhoods with coordinated gene expression. This includes the active and inactive X chromosomes. Using X chromosome inactivation as a working model, we utilized publicly available datasets together with a literature review to gain insight into topologically associated domains, lamin-associated domains, nucleolar-associating domains, scaffold/matrix attachment regions, and nucleoporin-associated chromatin and their role in regulating monoallelic expression. Furthermore, we comprehensively review for the first time the role of chromatin topology and nuclear architecture in the regulation of genomic imprinting. We propose that chromatin topology and nuclear architecture are important regulatory mechanisms for directing gene expression within imprinted domains. Furthermore, we predict that dynamic changes in chromatin topology and nuclear architecture play roles in tissue-specific imprint domain regulation during early development and differentiation.
Assuntos
Núcleo Celular/química , Cromatina/química , Impressão Genômica , Inativação do Cromossomo X , Animais , Diferenciação Celular , Núcleo Celular/metabolismo , Cromatina/metabolismo , Humanos , Camundongos , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , RNA Longo não Codificante/química , RNA Longo não Codificante/metabolismoRESUMO
Assisted reproductive technologies (ARTs) represent the best chance for infertile couples to conceive, although increased risks for morbidities exist, including imprinting disorders. This increased risk could arise from ARTs disrupting genomic imprints during gametogenesis or preimplantation. The few studies examining ART effects on genomic imprinting primarily assessed poor quality human embryos. Here, we examined day 3 and blastocyst stage, good to high quality, donated human embryos for imprinted SNRPN, KCNQ1OT1 and H19 methylation. Seventy-six percent day 3 embryos and 50% blastocysts exhibited perturbed imprinted methylation, demonstrating that extended culture did not pose greater risk for imprinting errors than short culture. Comparison of embryos with normal and abnormal methylation didn't reveal any confounding factors. Notably, two embryos from male factor infertility patients using donor sperm harboured aberrant methylation, suggesting errors in these embryos cannot be explained by infertility alone. Overall, these results indicate that ART human preimplantation embryos possess a high frequency of imprinted methylation errors.
Assuntos
Blastocisto/metabolismo , Metilação de DNA , Fertilização in vitro/efeitos adversos , Impressão Genômica , Adulto , Feminino , Humanos , Masculino , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Canais de Potássio de Abertura Dependente da Tensão da Membrana/metabolismo , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Proteínas Centrais de snRNP/genética , Proteínas Centrais de snRNP/metabolismoRESUMO
The embryonic pattern of global DNA methylation is first established in the inner cell mass (ICM) of the mouse blastocyst. The methyl donor S-adenosylmethionine (SAM) is produced in most cells through the folate cycle, but only a few cell types generate SAM from betaine (N,N,N-trimethylglycine) via betaine-homocysteine methyltransferase (BHMT), which is expressed in the mouse ICM. Here, mean ICM cell numbers decreased from 18-19 in controls to 11-13 when the folate cycle was inhibited by the antifolate methotrexate and to 12-14 when BHMT expression was knocked down by antisense morpholinos. Inhibiting both pathways, however, much more severely affected ICM development (7-8 cells). Total SAM levels in mouse blastocysts decreased significantly only when both pathways were inhibited (from 3.1 to 1.6 pmol/100 blastocysts). DNA methylation, detected as 5-methylcytosine (5-MeC) immunofluorescence in isolated ICMs, was minimally affected by inhibition of either pathway alone but decreased by at least 45-55% when both BHMT and the folate cycle were inhibited simultaneously. Effects on cell numbers and 5-MeC levels in the ICM were completely rescued by methionine (immediate SAM precursor) or SAM. Both the folate cycle and betaine/BHMT appear to contribute to a methyl pool required for normal ICM development and establishing initial embryonic DNA methylation.
Assuntos
Betaína-Homocisteína S-Metiltransferase/metabolismo , Blastocisto/metabolismo , Metilação de DNA , Embrião de Mamíferos/metabolismo , Ácido Fólico/metabolismo , Regulação Enzimológica da Expressão Gênica , S-Adenosilmetionina/metabolismo , 5-Metilcitosina/análise , Animais , Antimetabólitos Antineoplásicos/farmacologia , Betaína-Homocisteína S-Metiltransferase/antagonistas & inibidores , Blastocisto/citologia , Blastocisto/efeitos dos fármacos , Linhagem da Célula , Células Cultivadas , Embrião de Mamíferos/citologia , Embrião de Mamíferos/efeitos dos fármacos , Feminino , Imunofluorescência , Fígado/citologia , Fígado/efeitos dos fármacos , Fígado/metabolismo , Metotrexato/farmacologia , Camundongos , Proteínas Centrais de snRNP/metabolismoRESUMO
Many studies have shown that in vitro culture can negatively impact preimplantation development. This necessitates some selection criteria for identifying the best-suited embryos for transfer. That said, embryo selection after in vitro culture remains a subjective process in most mammalian species, including cows, mice and humans. General consensus in the field is that embryos that develop in a timely manner have the highest developmental competence and viability after transfer. Herein lies the key question: what is a timely manner? With emerging data in bovine and mouse supporting increased developmental competency in embryos with moderate rates of development, it is time to question whether the fastest developing embryos are the best embryos for transfer in the human clinic. This is especially relevant to epigenetic gene regulation, including genomic imprinting, where faster developing embryos exhibit loss of imprinted methylation, as well as to sex selection bias, where faster developmental rates of male embryos may lead to biased embryo transfer and, in turn, biased sex ratios. In this review, we explore evidence surrounding the question of developmental timing as it relates to bovine embryo quality, mouse embryo quality and genomic imprint maintenance, and embryo sex.
Assuntos
Técnicas de Cultura Embrionária/métodos , Transferência Embrionária/métodos , Desenvolvimento Embrionário/fisiologia , Fertilização in vitro/métodos , Animais , Bovinos , Epigênese Genética , Feminino , Humanos , Masculino , Camundongos , Pré-Seleção do SexoRESUMO
Genomic imprinting is an epigenetic process that distinguishes parental alleles, resulting in parent-specific expression of a gene or cluster of genes. Imprints are acquired during gametogenesis when genome-wide epigenetic remodeling occurs. These imprints must then be maintained during preimplantation development, when another wave of genome-wide epigenetic remodeling takes place. Thus, for imprints to persist as parent-specific epigenetic marks, coordinated factors and processes must be involved to both recognize an imprint and protect it from genome-wide remodeling. Parent-specific DNA methylation has long been recognized as a primary epigenetic mark demarcating a genomic imprint. Recent work has advanced our understanding of how and when parent-specific DNA methylation is erased and acquired in the germ line as well as maintained during preimplantation development. Epigenetic factors have also been identified that are recruited to imprinted regions to protect them from genome-wide DNA demethylation during preimplantation development. Intriguingly, asynchrony in epigenetic reprogramming appears to be a recurrent theme with asynchronous acquisition between male and female germ lines, between different imprinted genes, and between the two parental alleles of a gene. Here, we review recent advancements and discuss how they impact our current understanding of the epigenetic regulation of genomic imprinting.
Assuntos
Blastocisto , Desenvolvimento Embrionário , Epigênese Genética , Impressão Genômica , Células Germinativas , Animais , Feminino , Humanos , Masculino , CamundongosRESUMO
Genomic imprinting is a specialized transcriptional phenomenon that employs epigenetic mechanisms to facilitate parental-specific expression. Perturbations in parental epigenetic asymmetry can lead to the development of imprinting disorders, such as Beckwith-Wiedemann syndrome and Angelman syndrome. DNA methylation is one of the most widely studied epigenetic marks that characterizes imprinted regions. During gametogenesis and early embryogenesis, imprinted methylation undergoes a cycle of erasure, acquisition and maintenance. Gamete and embryo manipulations for the purpose of assisted reproduction are performed during these reprogramming events and may lead to their disruption. Recent studies point to the role of maternal-effect proteins in imprinted gene regulation. Studies are now required to increase understanding of how these factors regulate genomic imprinting as well as how assisted reproduction technologies may alter their function.
Assuntos
Síndrome de Angelman/genética , Síndrome de Beckwith-Wiedemann/genética , Metilação de DNA/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Impressão Genômica/genética , RNA Mensageiro Estocado/metabolismo , Técnicas de Reprodução Assistida , DNA (Citosina-5-)-Metiltransferase 1 , DNA (Citosina-5-)-Metiltransferases , Proteínas de Ligação a DNA , Feminino , Humanos , RNA Mensageiro Estocado/genética , Proteínas Repressoras , Fatores de Transcrição , Proteína 28 com Motivo TripartidoRESUMO
Gamete and early embryo development are important stages when genome-scale epigenetic transitions are orchestrated. The apparent lack of remodeling of differential imprinted DNA methylation during preimplantation development has lead to the argument that epigenetic disruption by assisted reproductive technologies (ARTs) is restricted to imprinted genes. We contend that aberrant imprinted methylation arising from assisted reproduction or infertility may be an indicator of more global epigenetic instability. Here, we review the current literature on the effects of ARTs, including ovarian stimulation, in vitro oocyte maturation, oocyte cryopreservation, IVF, ICSI, embryo culture, and infertility on genomic imprinting as a model for evaluating epigenetic stability. Undoubtedly, the relationship between impaired fertility, ARTs, and epigenetic stability is unquestionably complex. What is clear is that future studies need to be directed at determining the molecular and cellular mechanisms giving rise to epigenetic errors.
Assuntos
Epigênese Genética , Impressão Genômica , Instabilidade Genômica , Modelos Genéticos , Técnicas de Reprodução Assistida , Animais , Ectogênese , Feminino , Humanos , Infertilidade Feminina/genética , Infertilidade Feminina/metabolismo , Infertilidade Feminina/terapia , Infertilidade Masculina/genética , Infertilidade Masculina/metabolismo , Masculino , Oogênese , Técnicas de Reprodução Assistida/efeitos adversos , Técnicas de Reprodução Assistida/veterinária , EspermatogêneseRESUMO
During preimplantation development, major epigenetic reprogramming occurs, erasing gametic modifications, and establishing embryonic epigenetic modifications. Given the plasticity of these modifications, they are susceptible to disruption by assisted reproductive technologies, including embryo culture. The current state of evidence is presented for the effects of embryo culture on global DNA methylation and histone modifications, retroviral silencing, X-inactivation, and genomic imprinting. Several salient points emerge from the literature; that culture in the absence of other procedures can lead to epigenetic perturbations; that all media are suboptimal; and that embryo response to in vitro culture is stochastic. We propose that embryos adapt to the suboptimal environment generated by embryo culture, including epigenetic adaptations, and that "quiet" embryos may be the least epigenetically compromised by in vitro culture.