Identification of a novel isoform of microphthalmia-associated transcription factor that is enriched in retinal pigment epithelium.
Mutations at the mouse locus encoding microphthalmia-associated transcription factor (Mitf) affect the development of many cell types, including retinal pigment epithelium (RPE), melanocytes, mast cells, and osteoclasts. Here we have identified a novel Mitf isoform, Mitf-a, and its human homologue MITF-A by cDNA cloning. MITF-A consists of 520 amino acid residues and differs in the amino-terminus from authentic melanocyte-type MITF (MITF-M). MITF-A mRNA is widely expressed and represents a predominant MITF isoform in cultured RPE cells, whereas MITF-M mRNA is exclusively expressed in melanocytes and melanoma cells. In situ hybridization analysis suggested that Mitf-a mRNA is enriched in the prospective RPE of mouse embryo. Moreover, transient cotransfection assays suggested that MITF-A activated transcription of the tyrosinase and tyrosinase-related protein 1 genes. MITF-A/Mitf-a therefore may play an important role in melanogenesis in RPE.
Amae
S
S
Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Miyagi, Japan.
Fuse
N
N
Yasumoto
K
K
Sato
S
S
Yajima
I
I
Yamamoto
H
H
Udono
T
T
Durlu
Y K
YK
Tamai
M
M
Takahashi
K
K
Shibahara
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry*; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D017403:In Situ Hybridization; D008562:Membrane Glycoproteins; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000235:genetics; D009363:Neoplasm Proteins; D010088:Oxidoreductases; D010857:Pigment Epithelium of Eye / Q000737:chemistry*; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C497234:MITF protein, human; D008562:Membrane Glycoproteins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D009363:Neoplasm Proteins; D011506:Proteins; D012333:RNA, Messenger; C064972:TFEB protein, human; D014157:Transcription Factors; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase