A targeting construct containing IRES, rat Ntrk3 cDNA, SV40 polyA, and a floxed PGK-neo was inserted after the first 40 bp of exon 2, deleting exons 3-6. Crossing with Actb-cre mice excised the floxed neo. Southern blot confirmed recombination. RT-PCR of dorsal root ganglia of heterozygotes shows expression of both Ntrk1 and the inserted Ntrk3. (J:92099)