Epigenetic Modifications Necessary for Normal Development Are Established During Oocyte Growth in Mice1

Abstract

The ability of maternal chromatin to support full-term development is attained during oocyte growth. The aim of this study was to identify when during the growth phase the maternal chromatin developed the capacity to support term development. Mature metaphase II-arrested oocytes that contained chromatin from oocytes at different stages of oocyte growth were constructed by micromanipulation. The oocytes were fertilized in vitro, developed to the blastocyst stage in vitro, and transferred to recipients to assay developmental potential. The results demonstrate, firstly, that the origin of the maternal chromatin has no effect on the rate of oocyte maturation, fertilization, or development to the blastocyst in vitro. Secondly we demonstrate that maternal chromatin is first competent to support development to term during the latter half of oocyte growth when oocytes are 60-69 microm in diameter in juvenile mice or 50-59 microm in diameter in adult mice. These data show that epigenetic modifications necessary for postimplantation development occur during a specific phase of oocyte growth.

Protein kinase a modulates Cdc25B activity during meiotic resumption of mouse oocytes

“…Hanging drop culture of the oocytes was performed at 37°C, in a humidified atmosphere with 5% CO 2 . Oocytes culture was performed in Waymouth's MB752/1 Media (Invitrogen) supplemented with 100 g/ml sodium pyruvate, 50 IU/ml penicillin, 50 g/ml streptomycin sulfate, 3 mg/ml bovine serum albumin (BSA, Fraction V), referred to as MB medium (Bao et al, 2000). dbcAMP is included in the culture where indicated.…”

Gamete imprinting: setting epigenetic patterns for the next generation

“…The findings suggested that oocyte genomes at different stages during oocyte growth are functionally different. Further nuclear transplantation studies on oocytes at different stages of growth, together with the examination of imprinted gene expression in the resulting embryos, provided evidence that imprint acquisition occurs during the postnatal oocyte growth phase, along with the suggestion that some genes gain their imprints earlier than others (Bao et al 2000;Obata and Kono 2002). Complementary bisulfite sequencing experiments have been used to directly characterise the methylation of four paternally expressed genes in oocytes at different stages of oocyte growth (Lucifero et al 2002(Lucifero et al , 2004a.…”

In vitro development of mouse fetal germ cells into mature oocytes

“…In mammals, parental imprinted memories persist in somatic cells after fertilization, and it is necessary for them to be erased and re-established during germ cell development to reflect the gender of the individual. The erasure process of genomic imprinting memory proceeds in mouse primordial germ cells (PGCs) from 10.5 to 11.5 dpc, and the maternal-specific imprints are established during oogenesis (Kaneko-Ishino et al 1995, Kono et al 1996, Miyoshi et al 1998, Obata et al 1998, 2002b, Bao et al 2000, Surani 2001, Lee et al 2002, Zwaka & Thomson 2005. The Igf2r gene, a maternally expressed imprinted gene, has been shown with a fully methylated pattern in the maternal allele and an unmethylated pattern in the paternal allele in somatic cells, and begins to be methylated in mouse oocytes after 13.5 dpc (Brandeis et al 1993).…”