PROBLEM TO BE SOLVED: To provide a null mutation nonhuman animal, e.g. NaV2 channel gene-deficient nonhuman animal, useful as a laboratory model animal of the overdose of salinity, exhibiting an intake performance of a common salt same as that by a wild type under a satiety condition of water, and exhibiting the intake performance of much hypertonic salinity compared to that by the wild type under a hunger condition of the water.
SOLUTION: A target vector is produced by screening a genome DNA library of a mouse by using a rat NaGc DNA as a probe, isolating the NaV2 gegne of the genome DNA, and transducing a marker gene such as a neo gene to the exon site of the NaV2. A chimera mouse of a genital system is produced by introducing the produced target vector into an ES cell, selecting the ES cell obtained by homological recombination, and using the ES cell line. The NaV2 knock out mouse is produced by hybridizing the heterozygote mice obtained by hybridizing the obtained chimera mouse with a wild-type mouse.