A rtTA gene modified to respond to less doxycycline was placed under the control of the human NPHS2 gene, which is only expressed in the podocytes of the kidney. In the same vector, a modified CMV promoter with a rtTA responsive element was used to drive the expression of cre recombinase. Sixteen founder mice were created, and one was selected for further breeding based on the doxycycline-induced expression of cre recombinase that was only detected in kidney podocyte cells.