Bovine opsin gene expression exhibits a late fetal to adult regulatory switch

• Published in: Journal of neuroscience research Vol. 40; no. 6; p. 728
• Main Authors: DesJardin, L E, Lockwood, M K, Hauswirth, W W
• Format: Journal Article
• Language: English
• Published: United States 15.04.1995
• Subjects: Aging - physiology; Animals; Cattle; Embryo, Mammalian - ultrastructure; Embryonic and Fetal Development; Female; Fetus - physiology; Gene Expression Regulation; Genes, Switch; Photoreceptor Cells - physiology; Retina - embryology; Rod Opsins - genetics; Sarcosine - analogs & derivatives; Sarcosine - pharmacology; Transcription, Genetic - drug effects
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.490400604

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.