Clonación, caracterización y análisis de la expresión de genes reloj en el lenguado senegalés, Solea senegalensis

Resumen

During the course of the evolution, living organisms have developed internal 24-h clocks that allow them to anticipate and adequate their physiology to daily changes in environment.These biological clocks characteristically remain functional even under artificial conditions where animals are deprived of environmental changes. The phase of these clocks is reset on a daily basis by signals such as light, temperature or food availability. The genetic bases of the endogenous clocks are complex interlocked feedback loops where Clock and Bmal genes act as positive regulators while Period and Cryptochrome genes form the negative regulators.Post-translational mechanisms also influence the functioning of the molecular oscillations. This autoregulatory mechanism represents a cell autonomous mechanism shared by most cell types and results in a cyclic, self-sustained expression of clock genes with an approximately 24-h period. In the present Doctoral Thesis, some components of the endogenous clock are investigated in an important commercial teleost fish such as the Senegalese sole, with the aim to understand the molecular clockwork machinery that sustain circadian rhythms in this species. For this purpose, the cDNA sequences of the clock genes Per1, Per2, Per3 and Clock have been isolated and molecularly characterized. We have analyzed the tissue expression pattern and daily rhythms of these genes in central and peripheral tissues such as the retina, the optic tectum, the diencephalon, the cerebellum and the liver. Moreover, we have localized the clock gene-expressing cells within the sole retina, a direct photoreceptive organ that contains an endogenous clock in most vertebrate species. In addition,we have addressed the developmental onset and entrainmentof the circadian clockwork during early development of sole either under light-dark cycles or under continuous light or dark conditions. The expression pattern of the four genes during sole metamorphosishas also been investigated, together with the effects of different transient photoperiod conditions in the daily rhythms of each gene.