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M. A. Walter, M. Strungaru, T. Footz, E. Deilhes, P. Belleau, V. Raymond, F. Berry; The Sodium-Dependent Dicarboxylate Transporter 3 Gene (SLC13A3) Is a Potential Downstream Target of the Axenfeld-Rieger PITX2 Transcription Factor. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1725.
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Mutations of the pituitary homeobox 2 (PITX2) transcription factor result in Axenfeld-Rieger Syndrome (ARS) and glaucoma. The identification of direct targets of PITX2 is necessary to understand the genetic mechanisms underlying ocular development and disorders including glaucoma. Here, we have identified and characterized the Solute carrier family 13 sodium-dependent dicarboxylate transporter member 3 (SLC13A3) as a potential gene directly regulated by PITX2.
A hormone-inducible PITX2 expression system was generated to identify genes directly regulated by PITX2. RNA from non-pigmented ciliary epithelial (NPCE) cells transfected with hormone-inducible PITX2, or a negative control, was subjected to microarray analyses using Affymetrix U133A arrays. Data were analyzed using dCHIP algorithms to detect significant differences in expression. Genes with significantly altered expression in multiple microarray experiments in the presence of PITX2 were subjected to in silico and biochemical analyses.
Microarray experiments revealed that PITX2 reproducibly and significantly altered the expression of 498 genes in NPCE cells. Ten of the 15 genes tested by Northern assays or RT-PCR displayed altered expression in the presence of PITX2. One of these potential PITX2 target genes, SLC13A3, was selected for further analyses. In silico analyses revealed that the SLC13A3 gene is highly conserved among species, contains PITX2 binding sites in its upstream region and it is expressed in the eye and brain. Reducing PITX2 expression in NPCE cells by siRNA resulted in reduced levels of SLC13A3.
Our results indicate that SLC13A3 is a potential direct downstream target of PITX2. Interestingly, SLC13A3 is localized on chromosome 20q12, at the same locus as the related transporter SLC4A11, mutations of which cause Congenital Hereditary Endothelial Dystrophy (CHED). Since corneal anomalies have been associated with both ARS and glaucoma, this locus is also a good candidate not only for ARS, but also for glaucoma.
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