Fgf13 Knockout mouse models

Fgf13, mouse ortholog of human FGF13, encodes an intracellular FGF homologous factor whose multiple N-terminal splice isoforms are generated from an X-linked locus and which acts through two distinct nonreceptor mechanisms: docking on the C-terminal tails of voltage-gated sodium channels including NaV1.6 to control inactivation and availability, and direct microtubule binding that stabilizes polymers during neuronal polarization and axon branching. It is also a thermal nociception regulator in sensory neurons and contributes to cardiomyocyte excitability. Human hemizygous loss-of-function variants cause X-linked intellectual disability with epilepsy and febrile seizure susceptibility, which makes patient-derived truncating or missense knockins, together with isoform-specific targeting, more informative than whole-gene deletion. Nulls are viable, permitting conditional floxed alleles with Nestin-Cre, Advillin-Cre, or Myh6-Cre to separate cortical, sensory, and cardiac contributions, and X-linkage requires careful hemizygous versus mosaic female design. Paralogs Fgf11, Fgf12, and Fgf14 share channel partners, so compound alleles clarify which factor sets the excitability endpoint being measured.

Whole body loss of Fgf13 gives the clearest readout when the question is whether the gene is required at all. Follow up tissue work can still move to a conditional allele if lethality or compensation appears.