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Identification of a Distal Enhancer for the Melanocyte-Specific Promoter of the MITF Gene

Authors

  • Ken-ichi Watanabe,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
    2. Department of Otorhinolaryngology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Kazuhisa Takeda,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Ken-ichi Yasumoto,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Tetsuo Udono,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Hideo Saito,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Katsuhisa Ikeda,

    1. Department of Otorhinolaryngology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Tomonori Takasaka,

    1. Department of Otorhinolaryngology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Kazuhiro Takahashi,

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Toshimitsu Kobayashi,

    1. Department of Otorhinolaryngology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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  • Masayoshi Tachibana,

    1. Research Institute, Saitama Cancer Center, Saitama 362-0806, Japan
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  • Shigeki Shibahara

    1. Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi 980–8575, Japan,
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Prof Shigeki Shibahara Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan. E-mail: shibahar@mail.cc.tohoku.ac.jp

Abstract

Waardenburg syndrome (WS) is characterized by deafness and hypopigmentation because of the lack of melanocytes in the inner ear and skin. WS type 2 is associated with mutations in the gene encoding microphthalmia-associated transcription factor (MITF) that is required for melanocyte differentiation. MITF consists of multiple isoforms with different N-termini, one of which is exclusively expressed in melanocytes, named MITF-M. Its N-terminus is encoded by exon 1M that is under the regulation of the melanocyte-specific (M) promoter. Here we identify a distal regulatory region of 298 bp, located 14.5 kb upstream from exon 1M, which enhances the M promoter activity in cultured melanoma cells. This enhancer activity depends on the proximal M promoter region (−120 to −46). The MITF-M distal enhancer (MDE), thus identified, contains the binding sites for SOX10, a transcription factor responsible for another type of WS, known as Waardenburg–Hirschsprung syndrome. Characterization of MDE has suggested SOX10 as one of factors that are involved in the function of MDE. A putative MDE counterpart is located 12 kb upstream from mouse exon 1M and its role is discussed in relevance to the pathogenesis of red-eyed white Mitf mi–rw mice that exhibit small red eyes and white coat. Moreover, by in situ hybridization analysis, we suggest that Sox10 and Mitf-M (mRNA) are expressed in melanoblasts migrating toward the otic vesicle (prospective inner ear) of mouse embryos but are separately expressed in different cell types of the newborn cochlea. Thus, SOX10 regulates transcription from the M promoter in a developmental stage-specific manner.

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