Meeting Abstract

S7-1.1  Sunday, Jan. 6  Metazoan circadian rhythm: an universal "Zeitgeber" existing from sponges to humans MÜLLER, W.E.G. *; WANG, X.H. ; University Medical Center, Mainz,; University Medical Center, Mainz, GERMANY

In higher metazoans, the 24 h periodicity in the environment contributed to the evolution of the molecular circadian clock. We studied the circadian clock circuit in the lowest metazoans, the sponges. First, we identified in the demosponge Suberites domuncula the enzyme luciferase which generates photons. Then very likely, the photos generated by luciferase are transmitted via the biosilica glass skeleton of the sponges and are finally harvested by cryptochrome, acting as photosensor. Therefore, we propose that this photoreception/phototransduction circuit functions as a nerve-cell like signal transmitting system. This could be certified by the fact that S. domuncula reacts to different light wavelengths with a differential gene expression of the transcription factor SOX. Recently, we succeeded to demonstrate that the sponges nocturnin is a light/dark controlled clock gene and shows a poly(A) specific 3’ exoribonuclease activity. qPCR analyses revealed that primmorphs, 3D cell aggregates, after transferred from light to dark, show a 10-fold increased expression of nocturnin gene. In contrast, the expression level of glycogenin decreases in the dark by 3- to 4-fold. Finally it is concluded that sponges are provided with the molecular circadian clock protein nocturnin which is highly expressed in the dark and controls in the dark the stability of a key metabolic enzyme, glycogenin. References: Müller et al. (2009) Cell Mol Life Sci 66: 537. * Müller et al. (2010) FEBS J 277: 1182. * Wiens et al. (2010) J Cell Biochem 111:1377–1389. * Wang et al. Soft Matter; in press. DOI:10.1039/C2SM25889G