Meeting Abstract

S7-1.7  Sunday, Jan. 6  Evolution of animal clock: an echinoderm prospective OLIVERI, P*; PETRONE , L; LERNER, A; MATTIELLO, T; University College London p.oliveri@ucl.ac.uk

Almost all living organisms show circadian rhythmicity. Endogenous time-keeping mechanisms that regulate daily physiological and behavioral processes are genetically encoded and show a conserved network structure. Comparative studies highlighted a transcriptional-translational oscillator (TTO) based on interlocking negative feedback loops as key circadian clock network architecture. Molecular and cellular components of circadian clocks have been extensively characterized in land animals such as mammals and insects. In contrast, less is known about clocks in marine organisms despite the fact that the marine environment is characterized by an interplay of multiple periodicities and complex life cycles. To better understand metazoan circadian clock evolution, we are undertaking a molecular analysis of clock genes and their expression in the sea urchin, S. purpuratus. A genome survey identified in sea urchin both protostome and deuterostome components indicating a more complex origin of the metazoan clock tool-kit. Our comparative genomic analysis revealed a high plasticity of negative players of the TTO during animal evolution. Temporal gene expression analysis during sea urchin development showed that almost all of the clock genes are maternally expressed with decay around blastula stage, consistently with a potential role in gametogenesis. Many of them are also expressed later in development and at free-living larval stages. However, we have found no evidence of oscillatory genes expression during embryonic development. On the contrary, fully differentiated larvae, once exposed to different light regimes, show circadian oscillations of few clock genes. Their cellular localization, using whole mount in situ hybridization, identifies a group of neurosensory cells, which might function as a main light sensory organ. In addition, expression of “clock” genes has been detected in adult tissues.