SHMT2 and chronic myelogenous leukemia, BCR-ABL1 positive: SHMT2 competent control CML cells predominantly displayed m + 1 dTTP, suggesting that most of 1C units originate in the mitochondria, whereas loss of SHMT2 resulted in majority m + 2 dTTP and almost complete depletion of the m + 1 dTTP isotopologue (Fig. 1h and Supplementary Fig. 2m).