RAD21 and leukemia: We found that cells harboring STAG2 mutations have roughly half as much SMC1A, SMC3, and RAD21 as otherwise isogenic cells with wild-type STAG2. This result is consistent with previous studies showing that myeloid leukemias with STAG2 mutations have less chromatin-bound cohesin than leukemias with wild-type STAG2 [10].