Similarly, while a link with lymphocyte activation is established, the molecular mechanism that underpins its ability to guard against leukemias and lymphomas in mice is not understood5,11,14 Moreover, while enrichment at Xi in female cells is striking (Xi-CIZ1), CIZ1 protein also occupies nucleus-wide foci in male and female somatic cells (focal-CIZ1)5, and is elevated in post-replicative male germ cells15 suggesting that it has additional functions unrelated to the inactive X-chromosome. The gene discussed is CIZ1; the disease is leukemia.