FGF18 and omphalocele: When only Fgf8 (n=18) or Fgf18 (n=30) were inactivated via TCre-mediated recombination, omphalocele never occurred, demonstrating a small but real effect from the loss of Fgf17. Having established that all three genes play a role, we continued the analysis in an Fgf17 null background.