A point mutation (ACC>ATG) was introduced by site-directed mutagenesis into exon 12 at position 4847 resulting in the amino acid substitution of methionine for threonine (T468M) and a floxed neomycin cassette was inserted within the following intron. Cre-mediated recombination removed the neomycin cassette. The amino acid substitution is a common mutation in Leopard syndrome.