Maternal Transcriptome Analysis of Medaka (Oryzias latipes) Embryos by Use of mRNA–seq

In this study, we investigated the transfer of maternal transcripts to embryos during the early stages of development in medaka (Oryzias latipes). Using mRNA–Seq, we analyzed gene expression levels in medaka embryos, focusing on maternal transcripts during embryonic development from immediately after fertilization to the 7^th day post–fertilization. We found that 1,560 transcripts were detected only in the early development stage and that the levels of these transcripts decreased as development progressed. MKRN4, a known medaka maternal transcript, was among the detected transcripts, as were CYP26A1 and NANOG. Our results show that CYP26A1 and NANOG are maternally transported from female fish and play an important role in embryonic development. In this study, we confirmed that using an mRNA–Seq time–course following embryonic development can be used to investigate maternal transcript transfer to embryos.