The creators used classical homologous recombination to remove both copies of the Leishmania major target of rapamycin (TOR3). This mutant was used to study TOR3’s suitability as a potential drug candidate.
Da Silva, L. M., & Beverley, S. M. (2010). Expansion of the target of rapamycin (TOR) kinase family and function in Leishmania shows that TOR3 is required for acidocalcisome biogenesis and animal infectivity. Proceedings of the National Academy of Sciences, 107(26), 11965-11970.