The ubiquitous CAG (chicken beta actin) promoter was used to drive cre-dependent expression of a modified Ptpn11 gene, which contains the amino acid substitution of arginine for glutamine at position 79, following removal of an intervening floxed chloramphenicol (cat) gene. The amino acid substitution results in an increase in phosphatase activity. Three lines were created and line 1 was used in subsequent experiments.