An FRT-flanked selection cassette with a 3' loxP site was inserted upstream of exon 2. An additional loxP site was inserted downstream of exon 8. Flp-mediated recombination removed the selection cassette and left exons 2 through 8 floxed. Cre-mediated recombination removed exons 2 through 8. ELISA confirmed the absence of protein expression in brain and spinal cords. (J:243041)