C/EBPbeta modulates the early events of keratinocyte differentiation involving growth arrest and keratin 1 and keratin 10 expression.
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.
Zhu
S
S
Molecular and Cellular Toxicology, Department of Toxicology, North Carolina State University, Raleigh, North Carolina 27695-7633, USA.
Oh
H S
HS
Shim
M
M
Sterneck
E
E
Johnson
P F
PF
Smart
R C
RC
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
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