Male founders are injected with ENU (N-ethyl-N-nitrosourea) and harem bred to females. The pups are genetically screened using the TILLING assay (an enzyme-based heteroduplex cleavage assay) as well as nucleotide sequencing to identify and characterize target genes possessing ENU-induced mutations. A 3bp deletion generates a mutation at TTC (del251F)of rat Agtr1b.