Variations in DNA (cytosine-5)-methyltransferase-1 expression during oogenesis and early development of the zebrafish

We report the determination of zebrafish DNA (cytosine-5-) methyltransferase ( dnmt-1) temporal and spatial patterns of expression in gonadal tissues and during early development. Only one dnmt-1 message of around 5 kb was observed in all tissues examined and its levels were highest in gonadal tissues. During the course of oogenesis, early oocytes contain significant amounts of dnmt-1 transcript while message abundance declines as oocytes mature. During early embryogenesis message levels remain low until the blastula stage. Methyltransferase enzyme assays reveal that the maternal dnmt-1 message accumulated during oogenesis is translated into protein presumably providing necessary dnmt-1 stockpiles to support early embryonic development prior to zygotic gene activation. Such spatial and temporal regulation of dnmt-1 expression suggests specific functions for the enzyme during oogenesis and early development of zebrafish.