title: RainbowEnhancers Regulate Restrictive Transcription in Teleost Green, Red, and Blue Cones.
abstract: Photoreceptor-specific transcription of individual genes collectively constitutes the transcriptional profile that orchestrates the structural and functional characteristics of each photoreceptor type. It is challenging, however, to study the transcriptional specificity of individual photoreceptor genes because each gene's distinct spatiotemporal transcription patterns are determined by the unique interactions between a specific set of transcription factors and the gene's owncis-regulatory elements (CREs), which remain unknown for most of the genes. For example, it is unknown what CREs underlie the zebrafishmpp5bponli(ponli) andcrumbs2b(crb2b) apical polarity genes' restrictive transcription in the red, green, and blue (RGB) cones in the retina, but not in other retinal cell types. Here we show that the intronic enhancers of both theponliandcrb2bgenes are conserved among teleost species and that they share sequence motifs that are critical for RGB cone-specific transcription. Given their similarities in sequences and functions, we name theponliandcrb2benhancers collectivelyrainbowenhancers.Rainbowenhancers may represent acis-regulatory mechanism to turn on a group of genes that are commonly and restrictively expressed in RGB cones, which largely define the beginning of the color vision pathway.SIGNIFICANCE STATEMENTDim-light achromatic vision and bright-light color vision are initiated in rod and several types of cone photoreceptors, respectively; these photoreceptors are structurally distinct from each other. In zebrafish, although quite different from rods and UV cones, RGB cones (red, green, and blue cones) are structurally similar and unite into mirror-symmetric pentamers (G-R-B-R-G) by adhesion. This structural commonality and unity suggest that a set of genes is commonly expressed only in RGB cones but not in other cells. Here, we report that therainbowenhancers activate RGB cone-specific transcription of theponliandcrb2bgenes. This study provides a starting point to study how RGB cone-specific transcription defines RGB cones' distinct functions for color vision.
authors.affiliation: Departments of Ophthalmology.
authors.forename: Wei
authors.initials: W
authors.lastname: Fang
authors.affiliation: Departments of Ophthalmology.
authors.forename: Chuanyu
authors.initials: C
authors.lastname: Guo
authors.affiliation: Departments of Ophthalmology, weix@upmc.edu.|Microbiology and Molecular Genetics, and.|Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Wei
mesh_terms: D000818:Animals; D055358:Cone Opsins / Q000235:genetics*; D005399:Fishes / Q000145:classification / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D013045:Species Specificity; D015533:Transcriptional Activation / Q000235:genetics*; D015027:Zebrafish / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D055358:Cone Opsins; D008565:Membrane Proteins; D029961:Zebrafish Proteins; C513142:crb2b protein, zebrafish
keywords: crumbs; nagie oko; photoreceptor; ponli; promoter; rainbow enhancer