title: Bovine opsin gene expression exhibits a late fetal to adult regulatory switch.
abstract: Rates of bovine photoreceptor gene transcription, as measured by nuclear run-on assays, exhibit gene-specific patterns of regulation. Here we investigate initiation and elongation in nuclear run-on assays with the use of sarkosyl to further understand the nature of these gene-specific elements. Opsin transcription, alone among several genes tested, proved sarkosyl-sensitive. This sensitivity is maximal in adult retinas, with inhibition first detected in mid-third trimester fetal retinas. Therefore, opsin transcription appears to involve different regulatory elements in adult and fetal retinas, implying a fetal to adult switch in the control of opsin gene expression. Although this regulatory switch is initially activated at a time when the fetal outer nuclear layer of the retina first achieves adult-like morphology, further maturation of opsin regulation takes place postpartum since levels of sarkosyl sensitivity are almost 5-fold greater in adult retinas compared to the 7.5 month fetus. We also show that the sarkosyl-induced reduction of opsin transcription is not due to prevention of de novo RNA polymerase II initiation in the run-on reaction, suggesting the detergent alters a positive-acting, postinitiation component of the transcriptional apparatus. Since levels of opsin transcription with sarkosyl are similar to those of the other visual transduction genes with or without sarkosyl, this detergent-sensitive transcriptional component appears to account for the singularly high, gene-specific rate of opsin transcription in retinal photoreceptor cells.
authors.affiliation: Department of Immunology, University of Florida, Gainesville, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: DesJardin
authors.forename: M K
authors.initials: MK
authors.lastname: Lockwood
authors.forename: W W
authors.initials: WW
authors.lastname: Hauswirth
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D002417:Cattle; D004622:Embryo, Mammalian / Q000648:ultrastructure; D005314:Embryonic and Fetal Development; D005260:Female; D005333:Fetus / Q000502:physiology*; D005786:Gene Expression Regulation; D005812:Genes, Switch; D010786:Photoreceptor Cells / Q000502:physiology; D012160:Retina / Q000196:embryology; D017299:Rod Opsins / Q000235:genetics*; D012521:Sarcosine / Q000031:analogs & derivatives / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D017299:Rod Opsins; C025231:sarkosyl; D012521:Sarcosine