Dupré Sandrine M, Burt Dave W, Talbot Richard, Downing Alison, Mouzaki Daphne, Waddington David, Malpaux Benoit, Davis Julian R E, Lincoln Gerald A, Loudon Andrew S I
Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
Endocrinology. 2008 Nov;149(11):5527-39. doi: 10.1210/en.2008-0834. Epub 2008 Jul 31.
The pars tuberalis (PT) of the pituitary gland expresses a high density of melatonin (MEL) receptors and is believed to regulate seasonal physiology by decoding changes in nocturnal melatonin secretion. Circadian clock genes are known to be expressed in the PT in response to the decline (Per1) and onset (Cry1) of MEL secretion, but to date little is known of other molecular changes in this key MEL target site. To identify transcriptional pathways that may be involved in the diurnal and photoperiod-transduction mechanism, we performed a whole genome transcriptome analysis using PT RNA isolated from sheep culled at three time points over the 24-h cycle under either long or short photoperiods. Our results reveal 153 transcripts where expression differs between photoperiods at the light-dark transition and 54 transcripts where expression level was more globally altered by photoperiod (all time points combined). Cry1 induction at night was associated with up-regulation of genes coding for NeuroD1 (neurogenic differentiation factor 1), Pbef / Nampt (nicotinamide phosphoribosyltransferase), Hif1alpha (hypoxia-inducible factor-1alpha), and Kcnq5 (K+ channel) and down-regulation of Rorbeta, a key clock gene regulator. Using in situ hybridization, we confirmed day-night differences in expression for Pbef / Nampt, NeuroD1, and Rorbeta in the PT. Treatment of sheep with MEL increased PT expression for Cry1, Pbef / Nampt, NeuroD1, and Hif1alpha, but not Kcnq5. Our data thus reveal a cluster of Cry1-associated genes that are acutely responsive to MEL and novel transcriptional pathways involved in MEL action in the PT.
垂体腺的结节部（PT）表达高密度的褪黑素（MEL）受体，并且被认为通过解读夜间褪黑素分泌的变化来调节季节性生理。已知昼夜节律时钟基因在PT中表达，以响应MEL分泌的下降（Per1）和开始（Cry1），但迄今为止，对于这个关键的MEL靶位点的其他分子变化知之甚少。为了确定可能参与昼夜和光周期转导机制的转录途径，我们使用从在长或短光周期下24小时周期的三个时间点宰杀的绵羊中分离的PT RNA进行了全基因组转录组分析。我们的结果显示，在明暗转换时，153个转录本在不同光周期之间表达存在差异，54个转录本的表达水平受到光周期更全面的影响（所有时间点合并）。夜间Cry1的诱导与编码NeuroD1（神经源性分化因子1）、Pbef / Nampt（烟酰胺磷酸核糖基转移酶）、Hif1alpha（缺氧诱导因子-1alpha）和Kcnq5（钾通道）基因的上调以及关键时钟基因调节因子Rorbeta的下调有关。通过原位杂交，我们证实了PT中Pbef / Nampt、NeuroD1和Rorbeta表达的昼夜差异。用MEL处理绵羊增加了PT中Cry1、Pbef / Nampt、NeuroD1和Hif1alpha的表达，但没有增加Kcnq5的表达。因此，我们的数据揭示了一组与Cry1相关的基因，它们对MEL有急性反应，以及PT中参与MEL作用的新转录途径。
