Fgfr4 Conditional Knockout mouse models

Fgfr4, mouse ortholog of human FGFR4, encodes the FGF receptor most distinguished by its endocrine ligand relationship, forming a complex with beta-klotho to serve as the hepatic receptor for FGF19 (mouse Fgf15), which represses CYP7A1 transcription and thereby closes the bile acid feedback loop from ileum to liver. Unlike other family members, FGFR4 undergoes limited receptor internalization and lacks IIIb and IIIc alternative splicing, simplifying allele design. The germline G388R polymorphism enhances STAT3 signaling and associates with cancer progression, FGF19 amplification with FGFR4 dependency defines a hepatocellular carcinoma subset targeted by covalent inhibitors such as fisogatinib and roblitinib, and FGFR4 sustains rhabdomyosarcoma. Null mice are viable with elevated bile acid pool and depleted gallbladder, and only show skeletal phenotypes when combined with Fgfr3 alleles, indicating real but limited redundancy. Use conditional hepatocyte nulls for bile acid and hepatocarcinogenesis questions, and humanized kinase domain knockins when covalent inhibitor cysteine reactivity must translate.

Tissue restricted knockout of Fgfr4 keeps wild type function everywhere else. Breeding is often more robust, and the setup mirrors patient biology where mutations arise in a subset of cells.