A targeting vector was designed to replace exons 39-40 of the leucine-rich repeat kinase 2 (Lrrk2) gene with a loxP-flanked neomycin resistance (neo) cassette. Correctly targeted ES cells were transiently transfected with a Cre recombinase expression plasmid to delete the neo cassette. Correctly targeted ES cells were injected into blastocysts and resulting chimeric mice were bred to C57BL/6NTac mice. (J:170000)