Generation of Nkx2.2:lacZ mice using recombination-mediated cassette exchange technology.

Nkx2.2 encodes a homeodomain transcription factor required for the correct specification and/or differentiation of cells in the pancreas, intestine, and central nervous system (CNS). To follow the fate of cells deleted for Nkx2.2 within these tissues, we generated Nkx2.2:lacZ knockin mice using a recombination-mediated cassette exchange (RMCE) approach. Expression analysis of lacZ and/or β-galactosidase in Nkx2.2(lacZ/+) heterozygote embryos and adults demonstrates that lacZ faithfully recapitulates endogenous Nkx2.2 expression. Furthermore, the Nkx2.2(lacZ/lacZ) homozygous embryos display phenotypes indistinguishable from the previously characterized Nkx2.2(-/-) strain. LacZ expression analyses in the Nkx2.2(lacZ/lacZ) homozygous embryos indicate that Nkx2.2-expressing progenitor cells within the pancreas are generated in their normal numbers and are not mislocalized within the pancreatic ductal epithelium or developing islets. In the CNS of Nkx2.2(lacZ/lacZ) embryos, LacZ-expressing cells within the ventral P3 progenitor domain display different migration properties depending on the developmental stage and their respective differentiation potential.