N6-methyladenosine dynamics during early vertebrate embryogenesis

Early vertebrate embryogenesis is characterized by extensive post-transcriptional regulation during the maternal-to-zygotic transition. The N 6-methyladenosine (m 6 A) modifications on mRNA have been shown to affect both translation and stability of transcripts. Here we investigate the m 6 A topology during early vertebrate embryogenesis and its association with polyadenylated mRNA levels. The majority (>70%) of maternal transcripts harbor m 6 A, and there is a substantial increase of m 6 A in the polyadenylated mRNA fraction between 0 and 2 hours post fertilization. Notably, we find strong associations between m 6 A, cytoplasmic polyadenylation and translational efficiency prior to zygotic genome activation (ZGA). Interestingly, the relationship between m 6 A and translation is strongest for peaks located in the 3’UTR, but not overlapping stop codons. Sequence analyses revealed enrichment of motifs for RNA binding proteins involved in translational regulation and RNA degradation. After ZGA, m 6 A seem to diminish the effect of miR-430 mediated degradation. The reported results improve our understanding of the combinatorial code behind post-transcriptional mRNA regulation during embryonic reprogramming and early differentiation.