Defective Ureagenesis in Mice Carrying a Liver-specific Disruption of Hepatocyte Nuclear Factor 4α (HNF4α)

Abstract

Hepatocyte nuclear factor 4␣ (HNF4␣) regulates the expression of many genes preferentially expressed in liver. HNF4␣-null mice die during embryogenesis precluding the analysis of its function in the adult. To circumvent this problem, liver-specific HNF4␣-null mice were produced. Mice lacking hepatic HNF4␣ expression exhibited increased serum ammonia and reduced serum urea. This disruption in ureagenesis may be explained by a marked decrease in expression and activity of hepatic ornithine transcarbamylase (OTC). To determine the molecular mechanisms involved in transcriptional regulation of the mouse OTC gene, the OTC promoter region was analyzed. Sequence analysis revealed the presence of two putative HNF4␣-binding sites in the mouse OTC promoter region. By using transient transfection analysis, it was established that high levels of promoter activity were dependent on both HNF4␣-binding sites and the expression of HNF4␣. Furthermore, the proximal HNF4␣-binding site was found to be more important than the distal one for transactivating OTC promoter. These data demonstrate that HNF4␣ is critical for urea homeostasis by direct regulation of the OTC gene in vivo.The liver plays an important role in the metabolism of carbohydrates, proteins, lipids, vitamins, and hormones, the synthesis and excretion of bile acids, the production of blood coagulation factors and plasma proteins, and the detoxification of various xenobiotics. Most of these functions are achieved by hepatocytes that account for over 60% of the liver mass. The expression of genes preferentially expressed in liver is controlled by liver-enriched transcription factors (LETF)

Hepatocyte Nuclear Factor 4α Is a Central Regulator of Bile Acid Conjugation

“…Gel Shift Analysis-Crude nuclear extracts were prepared, and gel shift analysis was carried out as described previously (11). The following three double-stranded probes were used: HNF4␣-binding site for the mouse VLACSR promoter (wild-type), 5Ј-acaaaAGGACAGAGTCCAtgggt-3Ј and 5Ј-acccaTGGACTCTGTCCTtttgt-3Ј, the mouse VLACSR promoter (mutant), 5Ј-acaaaCTGACAGAGTCCAtgggt-3Ј and 5Ј-acccaTGGACTCTGTCAGtttgt-3Ј (mutations in the HNF4␣-binding site are boldface and underlined); GC box for the mouse VLACSR promoter (wild-type), 5Ј-tgtccaagGGGGCGGGGCag-3Ј and 5Ј-ctGCCCCGCCCCcttggacaC-3Ј, HNF4␣-binding site for the mouse VLACSR promoter (mutant), 5Ј-tgtccaagTAAAGAAGTGag-3Ј and 5Ј-ctCACTTCTTTAct-FIG.…”

Hepatocyte Nuclear Factor 4α Transactivates the Mitochondrial Alanine Aminotransferase Gene in the Kidney of Sparus aurata

“…In this study, we demonstrated that HNF4α interacts specifically with the HNF4 aminotransferase and alpha 1-antitrypsin (Monaci et al, 1988;Kimura et al, 1993;Inoue et al, 2002). Interestingly, HNF4α did not enhance the transcriptional activity of the previously cloned S. aurata cALT promoter (Anemaet et al, 2010) in HEK293 cells (data not shown), which suggest that HNF4α exerts a specific effect on the mALT gene.…”

“…HNF4 plays a key role for the accurate expression of genes involved in amino acid and protein metabolism (Monaci et al, 1988;Kimura et al, 1993;Inoue et al, 2002). There is evidence that HNF4α gene expression is reduced in the kidney of patients with diabetic nephropathy (Niehof and Borlak, 2008) (Nitsch et al, 1993;Nishiyori et al, 1994), we considered that HNF4α could play a role in the transcriptional control of mALT gene.…”

“…In fish liver, expression of cALT2 is associated with enhanced gluconeogenesis, while cALT1 is predominant during postprandial utilization of dietary nutrients (Anemaet et al, 2008(Anemaet et al, ). 5 al., 2000Hayhurst et al, 2001;Inoue et al, 2002;Parviz et al, 2003), regulate epithelial differentiation in the colon (Garrison et al, 2006) and control insulin secretion (Gupta et al, 2005;Miura et al, 2006), as well as to respond to increased metabolic demand in pancreatic β-cells (Gupta et al, 2007). In contrast, the physiological role of HNF4α in other organs, especially in the kidney, remains largely unknown.…”

“…These findings indicate that the minimal core promoter of the S. aurata mALT gene is located within 49 bp upstream from the transcriptional start, which suggests that cis-acting elements may be located in this region. Due to the fact that the promoter sequence of piscine mALT has several putative HNF4α boxes, and that HNF4α is involved in transcriptional regulation of several amino acid metabolism regulatory enzymes (Monaci et al, 1988;Nitsch et al, 1993;Inoue et al, 2002), this study was focused on the effect of HNF4α on the promoter activity of Sparus aurata mALT.…”