Ventii et al. (2008) demonstrated that missense mutations within the catalytic domain of BAP1 reduced tumour suppressor activity, but not protein expression, in a human NSCLC cell line. This highlights the fact that the presence of nBAP1 protein expression does not rule out the possibility of abnormalities in BAP1 function per se. Of note, although BAP1 knockout mice develop a myelodysplastic disorder with features of chronic myelomonocytic leukaemia (CMML), in human CMML, mutation of BAP1 is rare but that of the BAP1 interacting protein ASXL1 is very common (Dey et al., 2012). Here, ASXL1 is linked to monocytic leukemia.