A targeting vector was designed to insert nucleotide substitutions to result in T89M (the equivalent of human T93M found in SLOS patients) and a silent polymorphism creating a FspI restriction endonuclease site in exon 4. LoxP sites were inserted to flank exons 5-7. A neo with a 5' loxP site was inserted upstream of the intron 4 loxP site. (J:106758)