A M Diehl1, P Michaelson, S Q Yang. 1. Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Abstract
BACKGROUND/AIMS: Recent evidence suggests that CCAAT/enhancer binding protein (C/EBP) transcription factors may regulate hepatocyte terminal differentiation. METHODS: To explore this possibility, the present study looked for variations in the expression or DNA binding activity of different C/EBP isoforms during rat postnatal liver development and determined which of the C/EBPs were expressed by adult hepatocytes in primary culture. RESULTS: In intact rats, hepatocyte proliferation is active for 2-3 weeks after birth. During this period of postnatal liver growth, several liver-specific functions emerge and C/EBP alpha, beta, and delta isoforms are induced. Nuclear expression of the 36-kilodalton C/EBP delta protein increases immediately after birth, followed first by increases in the 38-kilodalton C/EBP beta protein expression and then by increases in the 42-kilodalton C/EBP alpha protein expression. Changes in C/EBP DNA binding activity accompany developmental increases in C/EBP proteins. Messenger RNAs of all three C/EBP isoforms are expressed by mature hepatocytes in primary culture. CONCLUSIONS: Specific C/EBP isoforms are induced differentially during the course of rat postnatal liver development. Young adult rats and cultured adult hepatocytes express all three C/EBP isoforms. These results are consistent with (but do not prove) the theory that variations in C/EBP expression and function help regulate hepatocyte terminal differentiation.
BACKGROUND/AIMS: Recent evidence suggests that CCAAT/enhancer binding protein (C/EBP) transcription factors may regulate hepatocyte terminal differentiation. METHODS: To explore this possibility, the present study looked for variations in the expression or DNA binding activity of different C/EBP isoforms during rat postnatal liver development and determined which of the C/EBPs were expressed by adult hepatocytes in primary culture. RESULTS: In intact rats, hepatocyte proliferation is active for 2-3 weeks after birth. During this period of postnatal liver growth, several liver-specific functions emerge and C/EBP alpha, beta, and delta isoforms are induced. Nuclear expression of the 36-kilodalton C/EBP delta protein increases immediately after birth, followed first by increases in the 38-kilodalton C/EBP beta protein expression and then by increases in the 42-kilodalton C/EBP alpha protein expression. Changes in C/EBP DNA binding activity accompany developmental increases in C/EBP proteins. Messenger RNAs of all three C/EBP isoforms are expressed by mature hepatocytes in primary culture. CONCLUSIONS: Specific C/EBP isoforms are induced differentially during the course of rat postnatal liver development. Young adult rats and cultured adult hepatocytes express all three C/EBP isoforms. These results are consistent with (but do not prove) the theory that variations in C/EBP expression and function help regulate hepatocyte terminal differentiation.
Authors: Gee Young Suh; Yang Jin; Ae-Kyung Yi; Xiao Mei Wang; Augustine M K Choi Journal: Am J Respir Cell Mol Biol Date: 2006-03-16 Impact factor: 6.914
Authors: T N Seagroves; S Krnacik; B Raught; J Gay; B Burgess-Beusse; G J Darlington; J M Rosen Journal: Genes Dev Date: 1998-06-15 Impact factor: 11.361