Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 3/7/2007
Citation: Qiu, G., Ramachandra, R.K., Rexroad III, C.E., Yao, J. Molecular Characterization and Expression Profiles of Cyclin B1, B2 and Cdc2 Kinase during Oogenesis and Spermatogenesis in Rainbow Trout (Oncorhynchus mykiss). Animal Reproduction Sciences 105:209-225. Interpretive Summary: In multicellular organisms, the development of gametes (oocytes and spermatocytes) is a complex process of development and differentiation, which is orchestrated by a stringent temporal and spatial expression of genes at both the transcriptional and translational levels. Successful execution of these highly ordered processes of oogenesis and spermatogenesis is critical to proper development. To better understand the orchestration of oocyte and spermatocyte development in rainbow trout, we focussed on characterizing three genes which are known to affect these processes in other animals. This included the cyclin B1, cyclin B2, and Cdc2 kinase genes. We examined their expression profiles during oogenesis and spermatogenesis at both the mRNA and protein levels. We observed that expression patterns of these genes are similar, but their proteins exhibit distinct profiles during gametogenesis. Our results indicate that cyclin B1 may play a principal role in regulating meiotic maturation of oocytes and spermatocytes.
Technical Abstract: The meiotic maturation of oocytes and spermatocytes is controlled by the maturation promotion factor (MPF), a complex of the Cdc2 and cyclin B proteins. To better understand the mechanism of oocyte and spermatocyte maturation in fish, the expression of cyclin B1 (CB1), cyclin B2 (CB2) and Cdc2 kinase during oogenesis and spermatogenesis in rainbow trout were examined at both the mRNA and protein levels. Quantitative real time PCR analysis showed that the expression of CB1 and CB2 mRNA was high at previtellogenesis and late vitellogenesis stages, but low at the early vitellogenesis stage and during early embryogenesis. Cdc2 mRNA was expressed constitutively throughout the processes of oogenesis and early embryogenesis except for a drop at early vitellogenesis. In situ hybridization analysis indicated that CB1, CB2 and Cdc2 transcripts were present in oocytes of different developmental stages as well as in all spermatogenic cells except for spermatogonia. Immunohistochemical analysis revealed that CB1 protein was absent in vitellogenic oocytes, but present in young previtellogenic oocytes. In contrast, CB2 and Cdc2 proteins were expressed in all stage oocytes. Similarly, CB2 and Cdc2 proteins were expressed throughout spermatogenesis, whereas CB1 protein was only detected in spermatogonia and spermatocytes, but not in spermatids. Thus, it appears that CB1, CB2 and Cdc2 transcripts display similar expression patterns during oogenesis and spermatogenesis, but CB1 protein is differentially expressed during these processes. These data suggest that CB1 may play a leading role in the regulation of meiotic maturation of oocytes and spermotocytes.