Since the whole-body HNF4α knockout is embryonic lethal and a liver-specific knockout results in death at six weeks of age due to dyslipidemia, high serum bile acid levels and ureagenesis defects (35, 92, 93), an HNF4α exon swap mouse model was developed to examine the effects of the HNF4α isoforms in vivo (94) (Figure 4A). Here, HNF4A is linked to metabolic syndrome.