title: Loss of genomic imprinting in mouse embryos with fast rates of preimplantation development in culture.
abstract: Currently, the stage of embryo development has been proposed as one of many criteria for identifying healthy embryos in infertility clinics with the fastest embryos being highlighted as the healthiest. However the validity of this as an accurate criterion with respect to genomic imprinting is unknown. Given that embryo development in culture generally requires an extra day compared to in vivo development, we hypothesized that loss of imprinting correlates with slower rates of embryonic development. To evaluate this, embryos were recovered at the 2-cell stage, separated into four groups based on morphological stage at two predetermined time points, and cultured to blastocysts. We examined cell number, embryo volume, embryo sex, imprinted Snrpn and H19 methylation, imprinted Snrpn, H19, and Cdkn1c expression, and expression of genes involved in embryo metabolism-Atp1a1, Slc2a1, and Mapk14-all within the same individual embryo. Contrary to our hypothesis, we observed that faster developing embryos exhibited greater cell numbers and embryo volumes as well as greater perturbations in genomic imprinting and metabolic marker expression. Embryos with slower rates of preimplantation development were most similar to in vivo derived embryos, displaying similar cell numbers, embryo volumes, Snrpn and H19 imprinted methylation, H19 imprinted expression, and Atp1a1 and Slc2a1 expression. We conclude that faster development rates in vitro are correlated with loss of genomic imprinting and aberrant metabolic marker expression. Importantly, we identified a subset of in vitro cultured embryos that, according to the parameters evaluated, are very similar to in vivo derived embryos and thus are likely most suitable for embryo transfer.
authors.affiliation: Departments of Obstetrics & Gynecology, and Biochemistry, University of Western Ontario, Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: Brenna A
authors.initials: BA
authors.lastname: Market Velker
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Denomme
authors.forename: Mellissa R W
authors.initials: MR
authors.lastname: Mann
mesh_terms: D000818:Animals; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000378:metabolism; D019175:DNA Methylation / Q000502:physiology; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018392:Genomic Imprinting; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D048308:Mitogen-Activated Protein Kinase 14 / Q000378:metabolism; D011247:Pregnancy; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D055517:snRNP Core Proteins / Q000378:metabolism
chemical_list: C493965:Cdkn1c protein, mouse; D050761:Cyclin-Dependent Kinase Inhibitor p57; D051272:Glucose Transporter Type 1; C495678:Slc2a1 protein, mouse; D055517:snRNP Core Proteins; D048308:Mitogen-Activated Protein Kinase 14; C497344:Atp1a1 protein, mouse; D000254:Sodium-Potassium-Exchanging ATPase