To determine if this increased survival of BMT recipients bearing Gdpd3−/− retro-CML-LSK cells was due to an inability to produce mature leukaemia cells, we used flow cytometry to examine the frequency of BCR-ABL1/EGFP+ mature leukaemia cells in peripheral blood (PB). The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.