The HNF4A Q164X Mutation Impairs Transcriptional Activation in Vitro but Its Heterozygosity Suppresses Liver Tumorigenesis in Vivo

Hepatocyte nuclear factor 4 alpha (HNF4A) is a master regulator of hepatic differentiation and metabolism. Here, we identify and characterize a truncating Q164X mutation that impairs HNF4A transcriptional activity in vitro and causes embryonic lethality when homozygous. Functional assays revealed that the Q164X protein retains nuclear localization but exhibits severely reduced DNA binding and transcriptional activation. CRISPR-generated Q164X mice showed no viable homozygotes, confirming the essential role of HNF4A in early embryogenesis. Unexpectedly, heterozygous Q164X mutants displayed reduced liver tumorigenesis following diethylnitrosamine and high-fat diet treatment, despite downregulation of HNF4A target genes such as ApoB and Hnf1a . These results suggest that partial HNF4A deficiency may trigger compensatory metabolic networks that protect against carcinogenic stress. Collectively, our study establishes Q164X as a loss-of-function HNF4A mutation with paradoxical tumor-suppressive effects in vivo.