Oocyte IVM or vitrification significantly impairs DNA methylation patterns in blastocysts as analysed by single-cell whole-genome methylation sequencing

Reprod Fertil Dev. 2020 Apr;32(7):676-689. doi: 10.1071/RD19234.

Abstract

To explore the mechanisms leading to the poor quality of IVF blastocysts, the single-cell whole-genome methylation sequencing technique was used in this study to analyse the methylation patterns of bovine blastocysts derived from invivo, fresh (IVF) or vitrified (V_IVF) oocytes. Genome methylation levels of blastocysts in the IVF and V_IVF groups were significantly lower than those of the invivo group (P<0.05). In all, 1149 differentially methylated regions (DMRs) were identified between the IVF and invivo groups, 1578 DMRs were identified between the V_IVF and invivo groups and 151 DMRs were identified between the V_IVF and IVF groups. For imprinted genes, methylation levels of insulin-like growth factor 2 receptor (IGF2R) and protein phosphatase 1 regulatory subunit 9A (PPP1R9A) were lower in the IVF and V_IVF groups than in the invivo group, and the methylation level of paternally expressed 3 (PEG3) was lower in the V_IVF group than in the IVF and invivo groups. Genes with DMRs between the IVF and invivo and the V_IVF and IVF groups were primarily enriched in oocyte maturation pathways, whereas DMRs between the V_IVF and invivo groups were enriched in fertilisation and vitrification-vulnerable pathways. The results of this study indicate that differences in the methylation of critical DMRs may contribute to the differences in quality between invitro- and invivo-derived embryos.

MeSH terms

  • Animals
  • Blastocyst / metabolism*
  • Cattle / embryology*
  • Cryopreservation / veterinary*
  • DNA Methylation / genetics
  • DNA Methylation / physiology*
  • Female
  • Fertilization in Vitro / veterinary
  • In Vitro Oocyte Maturation Techniques*
  • Single-Cell Analysis / methods
  • Single-Cell Analysis / veterinary
  • Whole Genome Sequencing / methods
  • Whole Genome Sequencing / veterinary*