The fork head domain-containing gene family (Fox) comprises over 20 members in mammals and is defined by a conserved 110 amino-acid motif containing a winged helix structure DNA-binding domain. The members of this gene family have been implicated as key regulators of embryogenesis, cell cycling, cell lineage restriction and cancer. The Foxn2 gene (Ches1) is expressed in postgastrulation embryos in multiple tissues that serve as important signaling centers as well as end-stage-differentiated cell types that arise from different germ layers of the developing embryo. The dynamic and specific expression of Foxn2 during embryonic development suggest multiple independent roles for Foxn2 function during gestation.