This transgene expresses cre recombinase under the control of the human thyroid peroxidase gene promoter. Insulator sequences were placed upstream and downstream of the TPO-cre cassette. The insertion site was found to be between bp 12,372,316 and 12,372,324 on mouse chromosome 9, near Cntn5 and Jrkl, approximately 1.5 and 0.9 Mbp from the transgene, respectively (J:303278).