Single-cell bisulfite sequencing of fat-tailed dunnart (Sminthopsis crassicaudata) E9 pooled embryos
DNA methylation (5mC) is an epigenetic mark that plays a critical role in defining cell fate. Following fertilisation, DNA methylation inherited from gametes must be reprogrammed to establish totipotency and enable the parental-to-zygotic transition. To accomplish this, non-mammalian vertebrates such as zebrafish and medaka subtly reprogram maternal 5mC profiles while maintaining high methylation levels throughout embryogenesis. In contrast, eutherian mammals such as mouse and human undergo global 5mC erasure in both embryonic and extraembryonic lineages. However, while embryonic 5mC is rapidly re-established to high levels upon implantation, the trophectoderm, which gives rise to the placenta, displays sustained and conserved DNA hypomethylation, suggesting that this drastic 5mC erasure may be functionally linked to complex placentation in mammals. To clarify whether extensive post-fertilisation 5mC erasure co-evolved with placentation, we explored embryonic methylome dynamics in another lineage of placental mammals, the marsupials. To address this, we produced single-cell DNA methylation maps of the bilaminar blastocyst for an Australian marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata).