Identification of five variants of the Ap2s1 gene induced by ENU in male mice. Schematic representation of the genomic organization of the mouse Ap2s1 gene. The Ap2s1 gene consists of five exons with the start (ATG) and stop (TGA) codons located in exons 1 and 5, respectively. The 5 ENU‐induced variants identified from screening tissue‐DNA samples from >10,000 male mice treated with ENU are highlighted by dotted lines above the exons and introns. The variants are two missense substitutions, Tyr20 and Ile123Asn, located in exons 2 and 5, respectively, and three intronic variants located in introns 1, 2, and 4. The locations of the FHH3‐associated mutations (Arg15Cys, Arg15His, and Arg15Leu) in humans are shown below the exons and introns. This Arg15 residue, which is located in exon 2, is conserved in mouse. The locations of the primers in exon 1 and 3 to investigate the effects of the intron variant located in intron 2 (IVS2+2T>C) are shown by arrows (F [forward] and R [reverse] primers).