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D.-A. M. Pillers, B. Malmin, J. T. den Dunnen, D. R. Trune, J. Pang; Upregulation of Retinal Dystrophin Dp260 Transcription by Methylprednisolone is Mediated by Glucocorticoid Receptor. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3772.
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© ARVO (1962-2015); The Authors (2016-present)
The Duchenne muscular dystrophy (DMD) gene encodes several isoforms of dystrophin via either internal or external promoters. Internal promoters are located within introns, and their regulatory mechanisms are not well described. Dp260, also known as retinal dystrophin, is a 260kDa isoform of dystrophin that is expressed in the outer-plexiform layer of the retina and is associated with normal retinal electrophysiology. We sought to characterize the Dp260 internal promoter within DMD intron 29 and to identify elements that regulate its expression.
The human Dp260 promoter region was cloned, sequenced, and analysed for potential regulatory elements. A luciferase reporter-promoter construct was transfected into cell lines and exposed to methylprednisolone and the glucocorticoid receptor (GR) antagonist RU486. Transcriptional activity was measured. Potential transcription factors were characterized by EMSA.
Two glucocorticoid response elements were identified by sequence analysis. Transcription was upregulated in Y79 (retinoblastoma), C2 (myoblast), and HeLa cells, but not in the GR-deficient COS-7 cell line. Transcription was blocked by RU486. EMSA showed a shift in the presence of a GRE DNA sequence and a supershift with anti-GRbeta.
The transcription of Dp260 can be manipulated by the use of steroid drugs and the effect is mediated by the glucocorticoid receptor binding to glucocorticoid response elements. This is of particular interest in the light of current steroid clinical treatment trials for DMD. An ability to manipulate Dp260 expression by pharmacogenetic means may have implications for the treatment of DMD and inherited disorders of night vision.
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