Coon S L, Bégay V, Falcón J, Klein D C
Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Biol Cell. 1998 Sep;90(5):399-405.
The photosensitive teleost pineal organ exhibits a daily rhythm in melatonin production. In most teleosts, including the pike, this is driven by an endogenous pineal clock. An exception is the trout, in which the pineal melatonin rhythm is a direct response to darkness. This fundamental difference in the regulation of melatonin production in two closely related species provides investigators a novel opportunity to study the molecular mechanisms of vertebrate clock function. We have studied the circadian regulation of mRNA encoding two melatonin synthesis enzymes by Northern blot analysis. These two enzymes are serotonin N-acetyltransferase (AA-NAT), the penultimate enzyme in melatonin synthesis, and tryptophan hydroxylase (TPH), the first enzyme in melatonin synthesis. A clock controls expression of both AA-NAT and TPH mRNAs in the pineal organ of pike, but not that of trout, in which the levels of these mRNAs are tonically elevated. A parsimoneous explanation of this is that a single circadian system regulates the expression of both AA-NAT and TPH genes in most teleosts, and that in trout this system has been disrupted, perhaps by a single mutation.
感光硬骨鱼的松果体器官在褪黑素分泌方面呈现出日节律。在大多数硬骨鱼中，包括狗鱼，这种节律是由内源性松果体生物钟驱动的。鳟鱼是个例外，其松果体褪黑素节律是对黑暗的直接反应。这两个亲缘关系密切的物种在褪黑素分泌调节上的这种根本差异，为研究脊椎动物生物钟功能的分子机制提供了一个新机会。我们通过Northern印迹分析研究了编码两种褪黑素合成酶的mRNA的昼夜节律调节。这两种酶分别是血清素N - 乙酰基转移酶（AA - NAT），它是褪黑素合成中的倒数第二个酶，以及色氨酸羟化酶（TPH），它是褪黑素合成中的第一个酶。生物钟控制狗鱼松果体器官中AA - NAT和TPH mRNA的表达，但不控制鳟鱼的，在鳟鱼中这些mRNA的水平持续升高。对此的一个简约解释是，在大多数硬骨鱼中，单一的昼夜节律系统调节AA - NAT和TPH基因的表达，而在鳟鱼中这个系统可能因单个突变而被破坏。
