The start codon, located in exon 2, was replaced with an AscI site to facilitate cloning of AscI-LoxP-EGFPf-3xpA-LoxP-DTR-pA-Frt-PGK-NeoR-Frt-AscI. Flp-mediated recombination removed the FRT-flanked selection cassette. Immunoblot analysis confirmed the absence of protein in dorsal root ganglion (DRG), spinal cord, hindpaw skin, and bladder tissue from adult homozygous mutant mice. Note: the knocked-in GFP was undetectable in mutant DRG and spinal cord neurons. (J:217933)