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Y. Liu, L. Fu, S.S. Deeb; Thyroid Hormone Regulates Genes Involved in Photoreceptor Function as Revealed by Expression Microarray Analysis of WERI Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4892.
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© ARVO (1962-2015); The Authors (2016-present)
Thyroid hormone receptor ß2 (TRß2) has been implicated in differentiation of middle and long wave–sensitive cones. We previously observed that triiodothyronine (T3) highly induces the L and M opsin genes in the human retinoblastoma cell line WERI–Rb1 cells. The purpose of this study was to identify other target genes for T3 in WERI cells that may be involved in photoreceptor differentiation and function.
WERI cells were cultured in RPMI 1640 medium with 2% B27 defined supplement and either treated with 100 nM T3or mock treated for 48 hours (triplicates). RNA was extracted and reverse transcribed, labeled and hybridized to Affymatrix human whole genome U133 plus 2.0 chips. The chip hybridization data were analyzed by ArrayAssist software (Stratagene) and a list of differentially expressed genes (≥ 2fold, p≤0.05) was generated using PLIER probe level analysis algorithm and T–test. Selected target genes identified were verified by Taqman–based real–time RT–PCR analysis.
We showed that WERI cells express high levels of TRß2 and its heterodimer partner retinoid X receptor γ. We profiled gene expression changes in WERI cells in response to T3 treatment by microarray analysis. Out of a total of about 54K probe sets tested, we found that 534 mRNA transcripts were significantly up–regulated, while 479 transcripts were significantly down–regulated after T3 treatment (fold≥ 2, p≤0.05). We verified the changes in 16 genes by quantitative real–time RT–PCR analysis. T3 up–regulates a set of genes involved in the cone phototransduction cascade, such as OPN1MW/LW, GNGT2, PDE6C, PDE6H, but down–regulates GNGT1, a gene that functions in rod phototransduction. Most of the other identified potential target genes of T3 are novel and several are implicated in human diseases.
We identified a significant number of novel target genes of thyroid hormone in human WERI cells. Among those are a set of genes involved in photoreceptor differentiation and phototransduction. This result supports the hypothesis that thyroid hormone/TRß2 positively regulate human cone photoreceptor differentiation.
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