Purchase this article with an account.
Tomohiro Masuda, Anitha Yerrabelli, Jose-Luis Linares, Anand Swaroop, Donald J. Zack; GTF2IRD1 Regulates Photoreceptor-specific Gene Expression. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2562.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
How cone opsin gene transcription is regulated is an important but incompletely answered question. Our objective was to identify transcription factors that promote expression of the cone opsin genes.
Yeast-one-hybrid (YOH) screening of a retinal cDNA library constructed from Nrl null mice was performed to identify transcription factors binding to the locus control region of the mouse M-cone opsin. Retinal expression of the identified transcription factor in the photoreceptors was confirmed by quantitative PCR of laser capture microdissected tissue, in situ hybridization, and immunohistochemistry. Western blotting with cell fractionation was used to examine nuclear localization of the factor in the retina. Functional analysis was performed by siRNA-mediated gene knockdown in primary murine retinal cells. Transient co-transfection of Gtf2ird1, Crx, and Nrl expression plamids with human L-cone opsin or bovine rhodopsin promoter luciferase reporter constructs was used to examine transcriptional activity.
Among the factors identified by the YOH screen was Gtf2ird1 (general transcription factor II-I repeat domain-containing protein 1), a helix-loop-helix (HLH) containing transcription factor that had not been previously implicated in retinal gene expression. Gtf2ird1 is observed first in the ganglion cells at postnatal day 0. As the retina develops, its expression expands to the cells in the inner nuclear and photoreceptor layers. Gtf2ird1 protein is localized in the nucleus. siRNA-mediated gene knockdown of Gtf2ird1 suppresses M-cone opsin expression. Moreover, other photoreceptor-specific genes, such as S-cone opsin and rhodopsin are also suppressed. Transient co-transfection assays showed that Gtf2ird1 enhanced both L-cone opsin and rhodopsin promoter activities synergistically with Crx, and Crx and Nrl, respectively.
These studies indicate that Gtf2ird1 is able to directly bind to human and mouse cone opsin promoters. The expression of Gtf2ird1 protein in photoreceptors was observed in late stages of retina development, after the cell fate of photoreceptors is determined. Functional analysis revealed that Gtf2ird1 regulates not only M-cone opsin but also other photoreceptor-specific genes. Taken together, our results implicate Gtf2ird1 as a transcription factor potentially involved in promoting and maintaining photoreceptor differentiation after cell fate is already determined by the action of other factors.
This PDF is available to Subscribers Only