Next, to investigate whether AMG900 induces a defect in mitotic progression in the absence of drug‐mediated SAC activation, we treated cells with AMG900 for 30 minutes and then checked recruitment of SAC‐related proteins to the kinetochore of prometaphase chromosomes, as determined by staining with CREST, an anti‐centromere autoantibody derived from serum of patients with CREST syndrome (limited scleroderma). Here, SS18L1 is linked to limited scleroderma.