AMH and Leydig cell tumor: However, the AMH-SV40Tag transgene is clearly expressed in both Leydig cells and Sertoli cells of SJL.AMH-SV40Tag transgenic mice (Fig. 4e) thereby implying that both cell types may express AMH and that transgene expression of SV40Tag may predispose to creation of tumors of either cell type with Sertoli cell tumors predominating in the original AT-t94 transgenic mouse generated in the C57BL/6 (H-2b) background strain and Leydig cell tumors predominating when the AMH-SV40Tag transgene is expressed in the SJL/J (H-2s) background strain.