title: Expression of the cyclin-dependent kinase inhibitor p27Kip1 by developing retinal pigment epithelium.
abstract: The cyclin-dependent kinase (Cdk) inhibitor p27Kip1 contributes to the timing of cell cycle withdrawal during development and, consequently, in organogenesis. Within the retina, this effector protein is up-regulated during the birth of neuronal and glial cells [Dev. Biol. (2000) 299]. However, its expression within the retinal pigment epithelium (RPE), a supporting cell layer that is essential for neural retina development and function, has not previously been reported. We show that p27Kip1 protein expression in the RPE occurs in two phases: an up-regulation during mid-to late embryonic stages and a down-regulation during the subsequent postnatal period. In the early phase of up-regulation, an inverse relationship is seen between expression of p27Kip1 and PCNA, an indicator of cycling cells. During both up-and down-regulation, the change in spatial pattern of expression proceeds in a central to peripheral manner, with p27Kip1 up-regulation paralleling retinal maturation. These data suggest that this cell cycle regulator may be an important factor controlling the timing of RPE cell cycle withdrawal.
authors.affiliation: Department of Anatomy and Cell Biology, James H Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA. defoe@mail.etsu.edu
authors.forename: Dennis M
authors.initials: DM
authors.lastname: Defoe
authors.forename: Edward M
authors.initials: EM
authors.lastname: Levine
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004791:Enzyme Inhibitors / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000196:embryology* / Q000378:metabolism*; D051381:Rats; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27