Analysis of 5-methyl cytosine and 5-hydromethyl cytosine content and distribution in bovine placental and fetal tissues after somatic nuclear reprogramming
Résumé
Objectives were to determine whether these early alterations are maintained during pregnancy. For that purpose, the content and distribution of 5-mC and 5-hmC were analyzed in different bovine cell line- ages during development. Bovine fetal (brain, liver, heart), extraembryonic (allantois, amnion) and placental (chorion and cotyledon) tissues were collected at day 60 of gestation from SCNT or from artificial insemination pregnancies. Methods: The global 5-mC content was determined by LUminometric Methylation Analysis, an approach using DNA genomic, enzyme cleavages (HpaII/MsepI/EcoRI) and pyrosequencing. The 5-hmC or 5-mC content was also measured using specific 5-hmC or 5-mC immunoassays. The tissular distribution of 5-mC and 5-hmC was analyzed by immunostaining with 5- mC and 5-hmC antibodies on paraffin sections. Result: Our data provide the first overview of the distribution of 5-mC and 5-hmC during the development in bovine. We observed a lower level of 5- mC in placental tissues compared with the embryonic and extraembryonic tissues from 30% to 90% of methylation (chorionic villi < chorion < liver < heart < brain < amnion < allantois). Somatic cloning induced an increase of the methylation level in chorionic villi only in late pregnancy stages. However, only the mesenchymal cells of the chorionic villi were immunostained for 5-mC and was involved in the methylation increase. In contrast, the 5hm-C content and the staining were more stable between the different lineages, suggesting a role of this epigenetic mark in all lineages in bovine. Conclusion: SCNT alters in a different manner the DNA methylation content in the cell lineages during the development.