USB1 and leukemia: In line with the substantial evidence that the zebrafish is an excellent system for the study of haematopoiesis during development23, our model, together with that recently generated by Patil et al. 24, demonstrate that the usb1 gene has a key role in normal haematopoiesis and, when dysfunctional, leads to significant reduction of mature mpx-neutrophils, making it a candidate for a leukaemia-causing gene.