RBPJ and myeloproliferative disorder: Mechanistically, RBPJ repressed miR-155, which repressed kB-Ras1 (NKIRAS1), a repressor of the NF-KB signaling pathway; deleting RBPJ in the niche therefore reduced NKIRAS1 expression and enhanced the NF-KB signaling, which correlated with MPN onset (Figure 1, left).