Section on Neuroendocrinology, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 2012 Jul 20;287(30):25312-24. doi: 10.1074/jbc.M112.356733.
MicroRNAs (miRNAs) play a broad range of roles in biological regulation. In this study, rat pineal miRNAs were profiled for the first time, and their importance was evaluated by focusing on the main function of the pineal gland, melatonin synthesis. Massively parallel sequencing and related methods revealed the miRNA population is dominated by a small group of miRNAs as follows: ~75% is accounted for by 15 miRNAs; miR-182 represents 28%. In addition to miR-182, miR-183 and miR-96 are also highly enriched in the pineal gland, a distinctive pattern also found in the retina. This effort also identified previously unrecognized miRNAs and other small noncoding RNAs. Pineal miRNAs do not exhibit a marked night/day difference in abundance with few exceptions (e.g. 2-fold night/day differences in the abundance of miR-96 and miR-182); this contrasts sharply with the dynamic 24-h pattern that characterizes the pineal transcriptome. During development, the abundance of most pineal gland-enriched miRNAs increases; however, there is a marked decrease in at least one, miR-483. miR-483 is a likely regulator of melatonin synthesis, based on the following. It inhibits melatonin synthesis by pinealocytes in culture; it acts via predicted binding sites in the 3"-UTR of arylalkylamine N-acetyltransferase (Aanat) mRNA, the penultimate enzyme in melatonin synthesis, and it exhibits a developmental profile opposite to that of Aanat transcripts. Additionally, a miR-483 targeted antagonist increased melatonin synthesis in neonatal pinealocytes. These observations support the hypothesis that miR-483 suppresses Aanat mRNA levels during development and that the developmental decrease in miR-483 abundance promotes melatonin synthesis.
微小 RNA（miRNAs）在生物调节中发挥着广泛的作用。在这项研究中，首次对大鼠松果体 miRNAs 进行了分析，并通过关注松果体的主要功能——褪黑素合成，评估了它们的重要性。大规模平行测序和相关方法揭示了 miRNA 群体主要由一小部分 miRNA 组成，约 75%由 15 种 miRNA 组成；miR-182 占 28%。除了 miR-182 之外，miR-183 和 miR-96 在松果体中也高度富集，这种模式在视网膜中也有发现。这项研究还鉴定了以前未被识别的 miRNAs 和其他小非编码 RNA。松果体 miRNAs 的丰度没有明显的昼夜差异，只有少数例外（例如，miR-96 和 miR-182 的丰度存在 2 倍的昼夜差异）；这与特征鲜明的 24 小时动态转录组模式形成鲜明对比。在发育过程中，大多数富集在松果体中的 miRNAs 的丰度增加；然而，至少有一种，miR-483 的丰度明显下降。基于以下几点，miR-483 很可能是褪黑素合成的调节剂。它通过预测结合位点抑制松果体细胞中的褪黑素合成；它作用于褪黑素合成的倒数第二酶——芳香族氨基酸 N-乙酰转移酶（Aanat）mRNA 的 3'-UTR，并且它的表达模式与 Aanat 转录物相反。此外，miR-483 的靶向拮抗剂增加了新生松果体细胞中的褪黑素合成。这些观察结果支持了这样的假设，即 miR-483 在发育过程中抑制 Aanat mRNA 水平，并且 miR-483 丰度的发育性下降促进了褪黑素的合成。
