SF3B1 and B-cell chronic lymphocytic leukemia: Extended analysis of other subset/non-subset cases and CLL cell lines confirmed our initial findings and led to the discovery of a novel BRD9 splice isoform with an alternative C-terminus, which could be induced by overexpression of mutated SF3B1. The alternative BRD9 isoform was shown to bind to the ncBAF complex and alter the interaction with auxiliary ncBAF complex proteins.