P0605Preliminary WGBS analysis of DNA methylation in ovine placentae from in vivo and in vitro produced embryos
Placentae were collected from 20-day-old fetuses obtained from natural conception (NF; N=5), in vitro fertilization in the presence (IVF+B12; N=5) or absence (IVF; N=5) of vitamin B12, which is essential for the biosynthesis of the methyl-donor S-adenosyl-methionine.
Epigenomes were analysed by Whole Genome Bisulfite Sequencing (Hiseq2000 Illumina). Bismark software v.0.14.3 was used to align each read to a bisulfite-converted sheep genome and to simultaneously call for cytosine methylation.
To date, 6 animals (2 per group) have been sequenced. An average of 35.7 million reads were produced per sample, with a mapping efficiency ranging from 76.8% to 79.3%. A lower proportion of methylated cytosineswas observed in the IVF compared to NF. Exceptions were the chromosomes OAR2, 9 and 11, where proportions were similar in the two groups.The addition of B12 further decreased methylation on all chromosomes, compared to IVF, with the notable exception of X chromosome, where for IVF+B12 the methylation proportion was higher than IVF. These data suggest that the in-vitro environment has an effect on the placental epigenome status which in turn may affect gene expression and the viability of in-vitro produced embryos. These preliminary data are to be confirmed with larger numbers and the methylation patterns along the genome have yet to be investigated.