title: KIT signaling regulates MITF expression through miRNAs in normal and malignant mast cell proliferation.
abstract: Activating mutations in codon D816 of the tyrosine kinase receptor, KIT, are found in the majority of patients with systemic mastocytosis. We found that the transcription factor, microphthalmia-associated transcription factor (MITF), is highly expressed in bone marrow biopsies from 9 of 10 patients with systemic mastocytosis and activating c-KIT mutations. In primary and transformed mast cells, we show that KIT signaling markedly up-regulates MITF protein. We demonstrate that MITF is required for the proliferative phenotype by inhibiting colony-forming units with sh-RNA knockdown of MITF. Furthermore, constitutively active KIT does not restore growth of primary MITF-deficient mast cells. MITF mRNA levels do not change significantly with KIT signaling, suggesting posttranscriptional regulation. An array screen from mast cells identified candidate miRNAs regulated by KIT signaling. We found that miR-539 and miR-381 are down-regulated by KIT signaling and they repressed MITF expression through conserved miRNA binding sites in the MITF 3'-untranslated region. Forced expression of these miRNAs suppressed MITF protein and inhibited colony-forming capacity of mastocytosis cell lines. This work demonstrates a novel regulatory pathway between 2 critical mast cell factors, KIT and MITF, mediated by miRNAs; dysregulation of this pathway may contribute to abnormal mast cell proliferation and malignant mast cell diseases.
authors.affiliation: Pediatric Hematology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA.
authors.forename: Youl-Nam
authors.initials: YN
authors.lastname: Lee
authors.forename: Stephanie
authors.initials: S
authors.lastname: Brandal
authors.forename: Pierre
authors.initials: P
authors.lastname: Noel
authors.forename: Erik
authors.initials: E
authors.lastname: Wentzel
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Mendell
authors.forename: Michael A
authors.initials: MA
authors.lastname: McDevitt
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
authors.forename: Melody
authors.initials: M
authors.lastname: Carter
authors.forename: Dean D
authors.initials: DD
authors.lastname: Metcalfe
authors.forename: Clifford M
authors.initials: CM
authors.lastname: Takemoto
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001549:Benzamides; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000068877:Imatinib Mesylate; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology* / Q000502:physiology*; D034721:Mastocytosis, Systemic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics* / Q000378:metabolism; D041681:NIH 3T3 Cells; D010879:Piperazines / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011743:Pyrimidines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; C497234:MITF protein, human; D035683:MicroRNAs; D051739:Microphthalmia-Associated Transcription Factor; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit; D019311:Staurosporine; C059539:midostaurin