U2AF1 and myelodysplastic syndrome: Our RNA-seq data should be interpreted with the caveats that U2AF1S34F expression levels (at a variant allele frequency [VAF] of >80%) in U2AF1S34F-transduced cells is higher than the level expected in MDS patients with heterozygous U2AF1 mutations (i.e., 50% VAF) and that the U2AF1S34F erythroid and granulomonocytic colonies analyzed contain some heterogeneity in the stage of differentiation (but they are nevertheless all fully committed toward either the myeloid or erythroid path).