Epigenetic marking systems confer stability of gene expression during mammalian development. Genome-wide epigenetic reprogramming occurs at stages when developmental potency of cells changes. At fertilization, the paternal genome exchanges protamines for histones, undergoes DNA demethylation and acquires histone modifications, whereas the maternal genome appears epigenetically more static. During preimplantation development, there is passive DNA demethylation and further reorganization of histone modifications. In blastocysts, embryonic and extraembryonic lineages first show different epigenetic marks. This epigenetic reprogramming is likely to be needed for totipotency, correct initiation of embryonic gene expression, and early lineage development in the embryo. Comparative works demonstrate that reprogramming is present in all the studied mammalian species, but the extent and timing varies, and this is consistent with the notable differences between species during preimplantation development. Parental imprinting marks originate in sperm and oocytes and are generally protected from this genome-wide reprogramming. Early primordial germ cells possess imprinting marks similar to those of somatic cells. However, rapid DNA demethylation after midgestation erases these parental imprints, in preparation for sex-specific de novo methylation during gametogenesis. Thus, by acting as an important molecular mark underlying the parental-specific expression of genes subjected to genomic imprinting, DNA methylation plays a significant role in regulating gamete maturation, fertilization, embryo growth and placental function. Even if recent studies have shown that complete DNA methylation of some imprinted genes occurs only at metaphase II (MII) stage, immature oocytes are highly methylated. The aim of this work was to compare the whole DNA methylation profile between human germinal vesicle (GV) oocytes and human MII oocytes retrieved after ovarian hyperstimulation, in order to investigate whether differences in the acquisition of an epigenetic profile should be related to the meiotic maturation stage. [...]
Whole DNA methylation in human oocytes evaluated by confocal laser scanning microscope.
GIOIA, Luisa;
2010-01-01
Abstract
Epigenetic marking systems confer stability of gene expression during mammalian development. Genome-wide epigenetic reprogramming occurs at stages when developmental potency of cells changes. At fertilization, the paternal genome exchanges protamines for histones, undergoes DNA demethylation and acquires histone modifications, whereas the maternal genome appears epigenetically more static. During preimplantation development, there is passive DNA demethylation and further reorganization of histone modifications. In blastocysts, embryonic and extraembryonic lineages first show different epigenetic marks. This epigenetic reprogramming is likely to be needed for totipotency, correct initiation of embryonic gene expression, and early lineage development in the embryo. Comparative works demonstrate that reprogramming is present in all the studied mammalian species, but the extent and timing varies, and this is consistent with the notable differences between species during preimplantation development. Parental imprinting marks originate in sperm and oocytes and are generally protected from this genome-wide reprogramming. Early primordial germ cells possess imprinting marks similar to those of somatic cells. However, rapid DNA demethylation after midgestation erases these parental imprints, in preparation for sex-specific de novo methylation during gametogenesis. Thus, by acting as an important molecular mark underlying the parental-specific expression of genes subjected to genomic imprinting, DNA methylation plays a significant role in regulating gamete maturation, fertilization, embryo growth and placental function. Even if recent studies have shown that complete DNA methylation of some imprinted genes occurs only at metaphase II (MII) stage, immature oocytes are highly methylated. The aim of this work was to compare the whole DNA methylation profile between human germinal vesicle (GV) oocytes and human MII oocytes retrieved after ovarian hyperstimulation, in order to investigate whether differences in the acquisition of an epigenetic profile should be related to the meiotic maturation stage. [...]I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
