@article{oai:az.repo.nii.ac.jp:00003892,
 author = {村上, 賢 and 舟場, 正幸 and Murakami, Masaru and Funaba, Masayuki},
 journal = {麻布大学雑誌, Journal of Azabu University},
 month = {Mar},
 note = {小眼球症関連転写因子（Mitf）は塩基性ヘリックス・ループ・ヘリックス-ロイシンジッパー（bHLH-LZ）構造を持つ組織特異的転写因子であり, 破骨細胞, マスト細胞, 神経堤由来メラノサイト, 網膜色素上皮細胞などの分化制御因子である。Mitfには, N末領域のみの配列が異なる少なくとも9種類のアイソフォーム（Mitf-A, -B, -C, -D, -E, -H, -J, -M, -mc）と, さらにエクソン6aの選択的スプライシングによる変異体（6abと6b）が存在することが知られている。本研究では, RAW264細胞を用いて, RANKL刺激による破骨細胞様細胞への分化におけるMitfの各アイソフォームと変異体の遺伝子発現および破骨細胞分化マーカー遺伝子の発現をRT-PCR, リアルタイムPCR, PCR-RFLP法により調べた。その結果, RANKL刺激によりMitf-Eの特徴的な遺伝子発現が認められた。また, RANKL刺激によりTRAP, カテプシンK, OSCAR, CTRの破骨細胞分化マーカー遺伝子が発現することを確認した。次に, 分化マーカー遺伝子の各制御領域をもつルシフェラーゼレポーターを用いて, 各Mitfアイソフォームの転写活性機能を比較したところ, TRAPレポーターに対してMitf-J/D/Eがわずかに転写活性を上昇させ, さらにc-junの共発現が相乗的効果を示すことがわかった。破骨細胞分化の後期過程においてMitfアイソフォームの特徴的な発現及びMitfとその他の転写因子との機能的相互作用が破骨細胞分化を制御しているのかもしれない。, Microphthalmia-associated transcription factor (Mitf), a member of the basic helix-loop-helix leucine zipper (bHLH-ZIP) transcription factors, is required for proper development of several cell lineages including osteoclasts, melanocytes, retinal pigment cells and mast cells. Mitf has been implicated to be a key regulator of the later steps of osteoclastogenesis, but the role of Mitf is not fully elucidated; although nine distinct Mitf isoforms, which contain an isoform-specific first exon and are identical exons 2 to 9, have been identified at the RNA level, it is unclear whether any isoforms are unique to the osteoclast lineage cells. Treatment of RAW264 macrophage-like cells with sRANKL (100 ng/ml) for 72 h resulted in the increase in the number of Trap-positive multinucleated cells. The present study examined expression of Mitf isoforms in sRANKL-induced osteoclast-like cells. The s-RANKL treatment induced robust expression of Mitf-E gene. In addition, Tfe3, another member of the bHLH-ZIP family, was also significantly expressed throughout the differentiation of RAW264 cells. E isoform of Mitfs may be involved in the regulation of the late process in osteoclast development. Previous studies have revealed that tartrate-resistant acid phosphatase (Trap) is a transcriptional target of Mitf in osteoclasts. Thus, we also examined factors affecting Trap gene transcription in HepG2 cells that are responsive to Mitf overexpression. Transcriptional activation assays using luciferase-based reporter gene containing Trap promoter (-2049 - +1) revealed that overexpression of Mitf-J/-D/-E but not Mitf-A slightly increased luciferase expression. The overexpression of c-Jun but not c-Fos and JunB increased expression of Trap reporter gene, and synergistic effects of c-Jun and Mitfs (-A and -J/-D/-E) on Trap gene transcription were detected. In contrast, no synergism was observed between Mitf and the other AP-1 component (c-Fos and JunB). Distinct expression of Mitf isoforms and functional interaction between Mitf and the other transcription factor such as c-Jun during the terminal differentiation of osteoclasts suggests discrete regulation of osteoclastogenesis., P(論文), 40016759568, 特集, application/pdf, FEATURE ARTICLES},
 pages = {89--91},
 title = {多様な分化制御転写因子Mitfの役割},
 volume = {17/18},
 year = {2009}
}