Loss of canonical Notch signaling in endothelial cells leads to MPN-like disease, through constitutive activation of mir-155 and NFKB signaling.63 Deletion of signal-induced proliferation-associated gene 1 (Sipa1) in mesenchymal and endothelial cells also results in MPN.64 Here, SIPA1 is linked to myeloproliferative neoplasm.