Developmental and Growth Hormone Regulation of the Expression of Liver-Enriched Transcription Factors in Bovine Liver
Liver gene expression changes during development and is affected by growth hormone (GH). These changes in gene expression may be due to the differential expression of the liver-enriched transcription factors (LETFs). To study the potential involvement of LETFs in the regulation of gene expression in the bovine liver, we cloned the cDNA fragments of nine bovine LETFs, including hepatocyte nuclear factor (HNF)-1Æ Ã , 1Æ Ã , 3Æ Ã , 3Æ Ã , 3Æ Ã , 6, albumin D-element binding protein (DBP), and CCAAT/enhancer-binding proteins (C/EBP) -Æ Ã and Æ Ã , and compared the expression levels of them between adult and fetal bovine liver and between GH-treated and untreated adult bovine liver. The mRNA abundance of the LETFs was determined by ribonuclease protection assay (RPA). The cloned bovine LETF cDNA sequences showed high degrees of similarity (79 % to 99 %) to the LETF sequences of other species. The mRNA levels of HNF-1Æ Ã , HNF-3Æ Ã , and HNF-6 were significantly higher (P < 0.05) in the fetal liver (n=3) than in the adult liver (n=7). There were significant increases (P < 0.05) in the mRNA expression of HNF-3Æ Ã and HNF-6 in the liver of cows 24 h (n=6) and 1w (n=6) after GH administration. The results of this study suggest that HNF-1Æ Ã , HNF-3Æ Ã , and HNF-6 may play a role in differential regulation of gene expression between the fetal and adult bovine liver and that HNF-3Æ Ã and HNF-6 may be also involved in GH regulation of gene expression in the bovine liver.