BCL9 is associated with B-cell acute lymphoblastic leukemia []. This entry includes BCL9 and BCL9L. They are tissue-specific transcriptional cofactors that cooperate with beta-catenin. In the nucleus, Bcl9 and Bcl9l simultaneously bind beta-catenin and the transcriptional activator Pygo2 to promote the transcription of a subset of Wnt target genes. They may also have a cytoplasmic role [].