In mammals, four types of Notch exist, Notch1–4, which all interact with ligands from the Delta and Jagged1 family.18 Intriguingly, Jagged1 expressed by endosteal cells has been shown to play a role in the bone colonisation by cancer cells.19 Most importantly, the Notch pathway accounts for the development of HSCs during embryogenesis,20 as well as for the stem cell maintenance of normal self-renewing or malignant stem cells.21,22. The gene discussed is JAG1; the disease is cancer.