An enhancer trap lentiviral transgenic approach was used to generate these mice. A lentiviral vector transgene construct contained an EGFP/cre fusion gene under control of the mouse Thy1.2 minimal promoter (-270 to +30). The vector was designed with a self-inactivating lentiviral backbone (FUGW). The packaged lentivirus was injected subzonally (under the zona pellucida) into 1-2 cell stage C57BL/6J embryos. Founder mice from line 16261 were crossed to B6-Gt(ROSA)26Sortm1Sor animals to assess cre activity/transmission. Cre positive mice were subsequently bred to C57BL/6 mice to generate a cre positive, reporter negative line.