transgenic rodents having ngf beta gene mutants in their genomes express ngf beta mutant proteins . the preparation methods of the transgenic rodents , the methods of utilizing the transgenic animals to prepare ngf beta mutant proteins and the resulting ngf beta mutant proteins are provided . the transgenic rodents are useful in preparing human ngf and in the study of the functions of ngf beta mutants and their receptors in the whole animal level , and also useful for screening and purifying ngf beta mutants which have high activity and high security .