Analysis of cohesin expression identifies a discrete subset of low expressors. (A) Expression of STAG2 in MDS and pAML subtypes. A discrete subset of patients exhibit low STAG2 expression defined as <2 standard deviations below the mean as compared with 17 healthy donors. This was more prevalent in patients with high-risk MDS and non–core binding factor AML without complex cytogenetics. (B) Percent of low expressors in cohesin genes. The frequency of cohesin low expressors for each cohesin complex gene (STAG2, RAD21, SMC1A, SMC3, STAG1, and PDS5B) is shown by disease subtype. STAG2 was most commonly underexpressed in high-risk MDS, whereas RAD21 was most commonly underexpressed in the remaining myeloid malignancies. SD, standard deviation.