ERC (European Research Council) Advanced Grant Research Group, Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55128 Mainz, Germany.
Biochem J. 2012 Dec 1;448(2):233-42. doi: 10.1042/BJ20120357.
Sponges are filter feeders that consume a large amount of energy to allow a controlled filtration of water through their aquiferous canal systems. It has been shown that primmorphs, three-dimensional cell aggregates prepared from the demosponge Suberites domuncula and cultured in vitro, change their morphology depending on the light supply. Upon exposure to light, primmorphs show a faster and stronger increase in DNA, protein and glycogen content compared with primmorphs that remain in the dark. The sponge genome contains nocturnin, a light/dark-controlled clock gene, the protein of which shares a high sequence similarity with the related molecule of higher metazoans. The sponge nocturnin protein was found showing a poly(A)-specific 3'-exoribonuclease activity. In addition, the cDNA of the glycogenin gene was identified for subsequent expression studies. Antibodies against nocturnin were raised and used in parallel with the cDNA to determine the regional expression of nocturnin in intact sponge specimens; the highest expression of nocturnin was seen in the epithelial layer around the aquiferous canals. Quantitative PCR analyses revealed that primmorphs after transfer from light to dark show a 10-fold increased expression in the nocturnin gene. In contrast, the expression level of glycogenin decreases in the dark by 3-4-fold. Exposure of primmorphs to light causes a decrease in nocturnin transcripts and a concurrent increase in glycogenin transcripts. It was concluded that sponges are provided with the molecular circadian clock protein nocturnin that is highly expressed in the dark where it controls the stability of a key metabolic enzyme, glycogenin.
海绵是滤食动物，它们需要消耗大量的能量来控制水通过水腔系统的过滤。已经表明，从偕老同穴海绵中制备的三维细胞聚集体 primmorphs 在体外培养时，会根据光照条件改变其形态。暴露在光线下，与仍在黑暗中的 primmorphs 相比，primorphs 的 DNA、蛋白质和糖原含量增加更快、更强。海绵基因组包含 nocturnin，一种光/暗控制的时钟基因，其蛋白质与高等后生动物的相关分子具有高度的序列相似性。发现海绵 nocturnin 蛋白具有聚（A）特异性 3'-外切核酸酶活性。此外，还鉴定了糖原合酶基因的 cDNA，用于后续的表达研究。制备了针对 nocturnin 的抗体，并与 cDNA 一起平行使用，以确定 nocturnin 在完整海绵标本中的区域表达；在水腔周围的上皮层中观察到 nocturnin 的表达最高。定量 PCR 分析显示，从光转移到暗的 primmorphs 中 nocturnin 基因的表达增加了 10 倍。相比之下，糖原合酶的表达在黑暗中减少了 3-4 倍。暴露于光下会导致 primmorphs 中 nocturnin 转录物减少和糖原合酶转录物增加。结论是，海绵具有高度表达的分子昼夜节律蛋白 nocturnin，它在黑暗中控制关键代谢酶糖原合酶的稳定性。
