Runx1 and Runx3 cooperatively repress Pmp22 to drive neurofibromagenesis [microarray]

Neurofibromatosis type 1 (NF1) patients are predisposed to develop neurofibromas but the underlying molecular mechanism(s) of neurofibromagenesis are not fully understood. We showed that dual genetic deletion of Runx1 (Rx1) and Runx3 (Rx3) in Schwann cells (SCs) and Schwann cell precursors (SCPs) significantly delayed neurofibromagenesis and prolonged mouse survival. We identified peripheral myelin protein 22 (Pmp22/Gas3) related to tumor initiation. Knockdown of Pmp22 with shRNAs increased Rx1fl/fl;Rx3fl/fl;Nf1fl/fl;DhhCre sphere numbers and enabled significantly more neurofibroma like micro-lesions on transplantation. Conversely, overexpression of Pmp22 in mouse neurofibroma SCs decreased proliferation. Mechanistically, Rx1/3 regulated alterative Pmp22 promoter usage and reduced post transcriptional expression of Pmp22. Finally, pharmacological inhibition of Runx/core binding factor beta (Cbf-β) activity significantly reduced neurofibroma volume in vivo. Thus, we identified a novel signaling pathway involving Rx1/3 suppression of Pmp22 in neurofibroma initiation and/or maintenance. Targeting disruption of Runx/Cbf-β interaction might provide a novel therapy for neurofibroma patients. EGFR- and + Schwann cell stem cell were selected for RNA extraction and hybridization on Affymetrix microarray.