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Xiaodong Zhang, Philip Andrew Ruzycki, Anne Hennig, Mingyan Yang, Shiming Chen; TFIIH-ERCC2 Is Essential For Photoreceptor Gene Expression and Development. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3589.
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© ARVO (1962-2015); The Authors (2016-present)
ERCC2, an essential component of the TFIIH general transcription factor complex, was identified as a co-factor of photoreceptor transcription factors (PhTFs) including CRX and NR2E3. TFIIH is known to play a role in DNA repair and transcription. Mutations in TFIIH-ERCC2 cause syndromic diseases with ocular defects and photosensitivity. The goal of this research was to use mouse models to determine the role of TFIIH-ERCC2 in photoreceptor gene transcription, development and disease.
ERCC2 interactions with PhTFs were investigated by co-immunoprecipitation and chromatin immunoprecipitation (ChIP). ERCC2’s function in the retina was determined using Cre/LoxP-mediated conditional knockout and phenotype assessment for changes in morphology (histology and immunohistochemistry), function (ERG) and gene expression (qRT-PCR).
ERCC2 co-localizes with PhTFs in photoreceptor nuclei, and physically interacts with them. ERCC2 co-immunoprecipitated with CRX and/or NR2E3 in retinal extracts of wild-type (WT) mice, but not control extracts from mice lacking CRX or NR2E3. ChIP assays on P14 WT mouse retinas showed that ERCC2 binds to the promoter and coding regions of each opsin gene along with CRX/NR2E3. ERCC2 target binding was reduced in mutant retinas lacking either CRX or NR2E3, suggesting that ERCC2 is a co-regulator of PhTFs. Conditional deletion of TFIIH-Ercc2 in retinal progenitor cells using Chx10-Cre resulted in irregular morphology of the outer nuclear layer with whorls and rosettes at P14 and 4 weeks of age, while the inner retinal layers appeared less affected. The Ercc2 null retinas also underwent progressive photoreceptor degeneration. ERG “a” and “b” wave amplitudes were drastically reduced in dark and light adapted 1 month old Ercc2-knockout mice, suggesting these mice are blind. qRT-PCR detected altered expression of many photoreceptor genes in mutant retinas.
The TFIIH-ERCC2 co-activator complex is essential for photoreceptor gene expression, structural integrity and function. ERCC2 adopts this cell type specific function by interacting with key PhTFs on target genes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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