title: Mitf and Tfe3, two members of the Mitf-Tfe family of bHLH-Zip transcription factors, have important but functionally redundant roles in osteoclast development.
abstract: The Mitf-Tfe family of basic helix-loop-helix-leucine zipper (bHLH-Zip) transcription factors encodes four family members: Mitf, Tfe3, Tfeb, and Tfec. In vitro, each protein in the family can bind DNA as a homo- or heterodimer with other family members. Mutational studies in mice have shown that Mitf is essential for melanocyte and eye development, whereas Tfeb is required for placental vascularization. Here, we uncover a role for Tfe3 in osteoclast development, a role that is functionally redundant with Mitf. Although osteoclasts seem normal in Mitf or Tfe3 null mice, the combined loss of the two genes results in severe osteopetrosis. We also show that Tfec mutant mice are phenotypically normal, and that the Tfec mutation does not alter the phenotype of Mitf, Tfeb, or Tfe3 mutant mice. Surprisingly, our studies failed to identify any phenotypic overlap between the different Mitf-Tfe mutations. These results suggest that heterodimeric interactions are not essential for Mitf-Tfe function in contrast to other bHLH-Zip families like Myc/Max/Mad, where heterodimeric interactions seem to be essential.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Iceland, 101 Reykjavik, Iceland. eirikurs@hi.is
authors.forename: Eiríkur
authors.initials: E
authors.lastname: Steingrimsson
authors.forename: Lino
authors.initials: L
authors.lastname: Tessarollo
authors.forename: Bhavani
authors.initials: B
authors.lastname: Pathak
authors.forename: Ling
authors.initials: L
authors.lastname: Hou
authors.forename: Heinz
authors.initials: H
authors.lastname: Arnheiter
authors.forename: Neal G
authors.initials: NG
authors.lastname: Copeland
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Jenkins
mesh_terms: D000483:Alleles; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D056657:Cathepsin K; D002403:Cathepsins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D051379:Mice; D008810:Mice, Inbred C57BL; D051739:Microphthalmia-Associated Transcription Factor; D009154:Mutation; D010010:Osteoclasts / Q000502:physiology*; D010022:Osteopetrosis / Q000209:etiology; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; C069203:TFE3 protein, human; D014157:Transcription Factors; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K; C534132:Ctsk protein, mouse