To determine whether donor Sertoli cells can efficiently engraft in drug-depleted cords, we transplanted a purified population of Sertoli cells isolated by fluorescence-activated cell sorting (FACS) from an 6.5–10.5 days postpartum (dpp) Sox9-ECFP mouse testis (for analysis of this population, see Supplementary Fig. 6a, b) into an adult mouse testis prepared by injection of BC into the rete 4 days earlier (Fig. 3a). The gene discussed is SOX9; the disease is breast cancer.