The human NGF coding sequence with an arginine to tryptophan substitution at amino acid 100 (R100W) and loxP flanked NeoR/KanR cassette and PGK promoter replaced the mouse Ngf coding sequence via homologous recombination. The C to T transition at position 661 resulting in the R100W mutation is seen in patients with Hereditary Sensory and Autonomic Neuropathy type 5.