OI-KIP, a cyclin dependent kinase inhibitor, is expressed in developing and adult brain of the Medaka (Oryzias latipes)

We have isolated OI-KIP, anew member of CIP/ KIP family of cyclin-dependent kinase inhibitors (CDIs), from an expression screen in the medaka (Teleost ), and then analyzed its expression pattern in developing and adult brain b y in situ hybridization (ISH). To better define the expression profile of t his CDI during cell differentiation, we performed a double labeling with OI -KIP mRNA and antibodies against proliferating cell nuclear antigen (PCNA). In the optic tectum, expression of RNA encoding OI-KIP during early embryo genesis is largely associated with the start of cell differentiation in pro liferative zones; later in development, its expression is closely related t o cell cycle exit. In the adult brain, transcripts appeared also in postmit otic cells long after they have exited the cell cycle. So, they may play a role in maintenance of the quiescent state throughout life.