title: Regulation of photoreceptor gene expression by the retinal homeobox (Rx) gene product.
abstract: The retinal homeobox (Rx) gene product is essential for eye development. However little is known about its molecular function. It has been demonstrated that Rx binds to photoreceptor conserved element (PCE-1), a highly conserved element found in the promoter region of photoreceptor-specific genes such as rhodopsin and red cone opsin. We verify that Rx is co-expressed with rhodopsin and red cone opsin in maturing photoreceptors and demonstrate that Rx binds to the rhodopsin and red cone opsin promoters in vivo. We also find that Rx can cooperate with the Xenopus analogs of Crx and Nrl, otx5b and XLMaf (respectively), to activate a Xenopus opsin promoter-dependent reporter. Finally, we demonstrate that reduction of Rx expression in tadpoles results in decreases in expression of several PCE-1 containing photoreceptor genes, abnormal photoreceptor morphology, and impaired vision. Our data suggests that Rx, in combination with other transcription factors, is necessary for normal photoreceptor gene expression, maintenance, and function. This establishes a direct role for Rx in regulation of genes expressed in a differentiated cell type.
authors.affiliation: Center for Molecular and Human Genetics, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Pan
authors.forename: Reyna I
authors.initials: RI
authors.lastname: Martinez-De Luna
authors.forename: Chih-Hong
authors.initials: CH
authors.lastname: Lou
authors.forename: Srivamsi
authors.initials: S
authors.lastname: Nekkalapudi
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Kelly
authors.forename: Amy K
authors.initials: AK
authors.lastname: Sater
authors.forename: Heithem M
authors.initials: HM
authors.lastname: El-Hodiri
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000378:metabolism*; D012172:Retinaldehyde; D012243:Rhodopsin / Q000235:genetics* / Q000378:metabolism; D017299:Rod Opsins / Q000235:genetics* / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D017299:Rod Opsins; D029867:Xenopus Proteins; D012243:Rhodopsin; D012172:Retinaldehyde