Involvement of JNK in the embryonic development and organogenesis in zebrafish.

c-Jun N-terminal kinase (JNK) is one of the mitogen-activated protein kinases. Previous studies showed that the JNK is involved in signaling pathways initiating cell cycle, and eventually, causing apoptosis through persistent activation in mammals. In this article, it is further revealed that the jnk1 gene is closely related with the embryonic development and organogenesis in zebrafish. RT-PCR and Western blot analysis show that there were distinct expression patterns of JNK at the different developmental stages as well as in the various tissues in zebrafish. Knockdown of jnk1 by RNA interference (RNAi) resulted in high lethal, serious retardation and malformations of embryos in zebrafish. SP600125, a JNK-specific inhibitor, gives rise to high mortality in zebrafish, similar to that caused by the jnk1 RNA interference. SP600125 is also responsible for the severe abnormality of organs, especially the skeletal system, such as skull, mandible deficiency, and cyrtosis heterauxesis. The results also indicate that the inhibition of JNK by SP600125 suppresses the ovarian differentiation during the embryo development in zebrafish. Overall, our study demonstrates that the jnk1 gene is required for ovary differentiation and development in the zebrafish, and down-regulated JNK directly inhibits ovary differentiation during early ontogenetic stages.