BCL11B (B-Cell CLL/Lymphoma 11B) is a transcription factor that plays a key role in the development and differentiation of T-cells, as well as in neuronal development. Proper regulation of BCL11B is essential for immune function and brain development. Mutations or dysregulation of BCL11B have been associated with certain blood cancers, such as T-cell acute lymphoblastic leukemia, and with neurodevelopmental disorders.