title: C/EBPbeta modulates the early events of keratinocyte differentiation involving growth arrest and keratin 1 and keratin 10 expression.
abstract: The epidermis is a stratified squamous epithelium composed primarily of keratinocytes that become postmitotic and undergo sequential changes in gene expression during terminal differentiation. The expression of the transcription factor CCAAT/enhancer binding protein beta (C/EBPbeta) within mouse epidermis and primary keratinocytes has recently been described; however, the function of C/EBPbeta within the epidermal keratinocyte is unknown. We report here that transient transfection of mouse primary keratinocytes with a C/EBP-responsive promoter-reporter construct resulted in a sevenfold increase in luciferase activity when keratinocytes were switched to culture conditions that induce growth arrest and differentiation. Forced expression of C/EBPbeta in BALB/MK2 keratinocytes inhibited growth, induced morphological changes consistent with a more differentiated phenotype, and upregulated two early markers of differentiation, keratin 1 (K1) and keratin 10 (K10) but had a minimal effect on the expression of late-stage markers, loricrin and involucrin. Analysis of the epidermis of C/EBPbeta-deficient mice revealed a mild epidermal hyperplasia and decreased expression of K1 and K10 but not of involucrin and loricrin. C/EBPbeta-deficient primary keratinocytes were partially resistant to calcium-induced growth arrest. Analysis of terminally differentiated spontaneously detached keratinocytes or those induced to differentiate by suspension culture revealed that C/EBPbeta-deficient keratinocytes displayed striking decreases in K1 and K10, while expression of later-stage markers was only minimally altered. Our results demonstrate that C/EBPbeta plays an important role in the early events of stratified squamous differentiation in keratinocytes involving growth arrest and K1 and K10 expression.
authors.affiliation: Molecular and Cellular Toxicology, Department of Toxicology, North Carolina State University, Raleigh, North Carolina 27695-7633, USA.
authors.forename: S
authors.initials: S
authors.lastname: Zhu
authors.forename: H S
authors.initials: HS
authors.lastname: Oh
authors.forename: M
authors.initials: M
authors.lastname: Shim
authors.forename: E
authors.initials: E
authors.lastname: Sterneck
authors.forename: P F
authors.initials: PF
authors.lastname: Johnson
authors.forename: R C
authors.initials: RC
authors.lastname: Smart
mesh_terms: D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D020013:Calcium Signaling; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D000078404:Epidermal Cells; D053550:Keratin-10; D015603:Keratinocytes / Q000166:cytology*; D007633:Keratins / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000096:biosynthesis; D051379:Mice; D008817:Mice, Mutant Strains; D009687:Nuclear Proteins / Q000378:metabolism*; D011498:Protein Precursors / Q000096:biosynthesis; D015533:Transcriptional Activation
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; C507491:Krt10 protein, mouse; D008565:Membrane Proteins; D009687:Nuclear Proteins; D011498:Protein Precursors; C064554:loricrin; D053550:Keratin-10; C032253:involucrin; D007633:Keratins