title: Microphthalmia-associated transcription factor in the Wnt signaling pathway.
abstract: Microphthalmia-associated transcription factor (MITF) contains a basic helix-loop-helix and leucine-zipper (bHLH-LZ) structure and consists of many isoforms with different N-termini. Melanocyte-specific MITF isoform (MITF-M) is of particular interest, because a heterozygous mutation in the MITF gene is associated with Waardenburg syndrome type 2 (WS2) that is characterized by deafness and hypopigmentation because of lack of melanocytes in the inner ear and skin. Expression of MITF-M is under the regulation of the melanocyte-specific promoter (M promoter) of the MITF gene, and transcription from the M promoter is induced by Wnt signals through a nuclear mediator, lymphoid-enhancing factor 1 (LEF-1). In addition, functional cooperation of MITF-M with LEF-1 could lead to transcriptional activation of the M promoter and the dopachrome tautomerase (DCT) gene, an early melanoblast marker. The bHLH-LZ region of MITF-M is responsible for the physical interaction with LEF-1, and beta-catenin is required for the collaboration between LEF-1 and MITF-M. Importantly, MITF-M could function as a non-DNA-binding co-factor for LEF-1. These results suggest that MITF-M may function as a self-regulator of its own expression to maintain a threshold level of MITF-M at a certain sensitive stage of melanocyte development, which could account for the dominant inheritance of WS2. MITF-M therefore plays dual roles in the Wnt signaling pathway; MITF-M represents a downstream target and a nuclear mediator of Wnt signals in melanocytes.
authors.affiliation: Department of Molecular Biology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Saito
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yasumoto
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takeda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takahashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibahara
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005091:Exons; D005786:Gene Expression Regulation; D006579:Heterozygote; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000235:genetics; D051821:Lymphoid Enhancer-Binding Factor 1; D008544:Melanocytes / Q000378:metabolism; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor; D008954:Models, Biological; D008957:Models, Genetic; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C497573:LEF1 protein, human; C497574:Lef1 protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase