The targeting vector contains a floxed STOP cassette (LSL) inserted into intron 1, followed by a partial exon 2 fused to a human HIP1 (huntingtin interacting protein 1) cDNA, IRES-EGFP, and a polyadenylation signal sequence. An FRT-flanked neomycin cassette inserted after the poly(A) was removed by a Flp-expressing plasmid. Western blot analysis on lung tissue confirmed the absence of mouse Hip1 protein.