Two essential processes, oocyte maturation and ovulation, before oocytes become fertilizable that are independently induced but co-operatively proceeded at the final step in oogenesis. Eventhough these two processes are induced by same maturation-inducing steroid, 17, 20 beta-dihydroxy-4-pregnen-3-one (17, 20 beta-DHP), in teleost, the receptor for each pathway is suggested to be different and thus signal transduction pathways are different. While much progresses achieved on the molecular mechanisms for induction of oocyte maturation, the mechanisms to induce ovulation is under elucidation. Previously we established the procedure that can make it possible to prepare the ovarian tissue which contains oocyte maturation-induced oocytes in vivo. In the same way, ovulation can be induced in alive zebrafish. Thus it became possible to select the genes up-regulated according to ovulation by compare the gene expression between maturation-inducing genes in matured oocytes and both maturation and ovulation-inducing genes in ovulated eggs. In vivo bioassay has been applied to prepare maturated and ovulated ovarian samples. Specifically up-regulated genes to induce ovulation will be selected by RNA-seq analysis. The mRNA abundance of highly up-regulated genes will be confirmed by q-PCR analysis. By this project, ovulation-inducing genes will be selected and its roles in induction of ovulation will be addressed in the future.