Foxb1-driven Cre expression in somites and the neuroepithelium of diencephalon, brainstem, and spinal cord.

We have knocked-in Cre-IRES-EGFP in the Foxb1 locus by homologous recombination in embryonic stem cells. We removed the PGK-neo cassette (which was flanked by FRT sequences) by crossing with the FLPeR deleter mouse. The Foxb1(Cre) line showed Cre recombinase activity as well as EGFP fluorescence reproducing Foxb1 expression accurately. By crossing Foxb1(Cre) mice with the ROSA26R and Z/AP mouse reporter lines we have been able to trace the lineage of Foxb1-expressing cells. Early transient expression of Foxb1 in the paraxial mesoderm translates into labeling of the somites. In the central nervous system (CNS), the Foxb1 lineage includes the thalamus and mammillary body (hypothalamus), brainstem, and the ventral spinal cord and floor plate.