RGD Reference Report - Circadian regulation of hydroxyindole-O-methyltransferase mRNA levels in rat pineal and retina. - Rat Genome Database

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Circadian regulation of hydroxyindole-O-methyltransferase mRNA levels in rat pineal and retina.

Authors: Gauer, F  Craft, CM 
Citation: Gauer F and Craft CM, Brain Res 1996 Oct 21;737(1-2):99-109.
RGD ID: 1299464
Pubmed: PMID:8930356   (View Abstract at PubMed)

Hydroxyindole-O-methyltransferase (HIOMT, EC catalyzes the methylation of acetylserotonin to complete the synthesis of melatonin in the pineal and retina. A complete 1728 nucleotide cDNA encoding rat pineal HIOMT was isolated, characterized, and used to evaluate day/night levels of HIOMT mRNA. As previously reported for HIOMT enzyme activity, HIOMT mRNA levels were also greater in the pineal than in the retina. Northern blot analysis and in situ hybridization were useful for detection of HIOMT mRNA in the pineal but not the retina, whereas the reverse transcriptase-polymerase chain reaction or RNase protection assay revealed transcripts for HIOMT both in the pineal and retina. Investigating HIOMT mRNA levels in rat pineal and retina at 6 time-points throughout a 24 h period revealed higher levels of HIOMT message during darkness. The daily fluctuation in HIOMT mRNA persisted in constant darkness, verifying an endogenous circadian rhythm both in the pineal and retina. In mammalian pineals, sympathetic innervation, synthesizing norepinephrine that activates beta (beta) adrenergic receptors, entrain several circadian bodily functions through the synthesis and release of melatonin. A single injection of the beta-adrenergic agonist, isoproterenol, induced a dramatic increase of HIOMT mRNA levels in the light-adapted pineal, in vivo. Moreover, a single injection of the beta-adrenergic antagonist, propranolol, prevented the nocturnal increase of pineal HIOMT mRNA. Using a combination of methods, it has been shown that the level of HIOMT mRNA fluctuates daily in both the pineal gland and retina. This day/night rhythm can be modulated either by beta receptor agonists or antagonists when applied appropriately during the circadian cycle, suggesting that the mRNA changes in HIOMT may be controlled at the transcriptional level.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
melatonin biosynthetic process  IDA 1299464 RGD 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
acetylserotonin O-methyltransferase activity  IDA 1299464 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Asmt  (acetylserotonin O-methyltransferase)

Additional Information