title: Transcriptional regulation of hydroxyindole O-methyltransferase in the chicken pineal gland: day/night changes and long-term effects of light and darkness.
abstract: The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalysed by hydroxyindole O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. This transcriptional rhythm was not accompanied by day/night changes in HIOMT concentration, probably due to a slow turnover of this protein. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.
authors.affiliation: Laboratoire de Neurobiologie et Neuroendocrinologie Cellulaires, URA CNRS 290.
authors.forename: M
authors.initials: M
authors.lastname: Bernard
authors.forename: J
authors.initials: J
authors.lastname: Guerlotte
authors.forename: M
authors.initials: M
authors.lastname: Cogne
authors.forename: P
authors.initials: P
authors.lastname: Greve
authors.forename: J P
authors.initials: JP
authors.lastname: Collin
authors.forename: P
authors.initials: P
authors.lastname: Voisin
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000235:genetics*; D000818:Animals; D015152:Blotting, Northern; D002645:Chickens; D003624:Darkness; D005786:Gene Expression Regulation / Q000528:radiation effects*; D008027:Light; D010870:Pineal Gland / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D000121:Acetylserotonin O-Methyltransferase