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Pineal serotonin N-acetyltransferase: expression cloning and molecular analysis
S L Coon1, P H Roseboom, R Baler
1Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Science (New York, N.Y.)
|December 8, 1995
Summary
Researchers cloned ovine arylalkylamine N-acetyltransferase (AA-NAT), crucial for melatonin production. Ovine AA-NAT mRNA showed distinct daytime abundance and low rhythmicity compared to rats, suggesting species-specific circadian regulation.
Area of Science:
- Chronobiology
- Molecular Biology
- Neuroendocrinology
Background:
- Melatonin, a key hormone for circadian and seasonal rhythms in mammals, is synthesized via the enzyme arylalkylamine N-acetyltransferase (AA-NAT).
- Understanding the regulation of AA-NAT is crucial for deciphering mammalian circadian physiology.
Purpose of the Study:
- To clone the complementary DNA (cDNA) encoding ovine AA-NAT.
- To investigate the tissue distribution and circadian expression patterns of ovine AA-NAT mRNA.
Main Methods:
- Cloning of ovine AA-NAT cDNA using molecular biology techniques.
- Quantitative analysis of AA-NAT mRNA abundance in various ovine tissues (pineal gland, retina, pituitary, brain) across different times of day.
Main Results:
- Ovine AA-NAT cDNA was successfully cloned.
- AA-NAT mRNA was highly abundant in the ovine pineal gland during the day, with lower levels in the retina.
- Unexpectedly, AA-NAT mRNA was also detected in the pituitary gland and certain brain regions.
- The night-to-day ratio of ovine pineal AA-NAT mRNA was low (less than 2), contrasting sharply with the high ratio observed in rats (exceeding 150).
Conclusions:
- Ovine AA-NAT is a member of a large acetyltransferase superfamily.
- The circadian regulation of AA-NAT mRNA in sheep appears significantly different from that in rats, highlighting species-specific mechanisms in melatonin synthesis and circadian timing.