| Abstract |
Circadian rhythms exist in many biochemical, physiological and cellular
processes, including hormonal synthesis and/or secretion. These rhythms
are driven by endogenous clocks that are ultimately entrained by
environmental factors, being the light-dark cycle (LD) the most important
synchronizer. Fish circadian rhythms appear sustained by cellautonomous
mechanisms, but unfortunately, fish cellular clocks have been poorly
studied in marine species. An important bottleneck in fish research is the
supply and maintenance of embryos, larvae, juvenile and adult specimens.
In this context, cell lines constitute powerful and alternative tools with
important applications in fish chronobiology and endocrinology. In this
study, we have used a recently developed monoclonal embryonic cell line
derived from the blastula stage of gilthead seabream embryos (SAEC-H7) to
analyse the oscillation of central clock components and the response to
different photoregimes. Our results showed rhythmic expression of key
clock genes in embryonic cells, which were able to re-entrain to a light
cycle inversion. Rhythmic expression of some core clock genes persisted
under constant light and dark conditions after several days, but with
decreased mesors and amplitudes, reinforcing the circadian and endogenous
nature of the cellular rhythms. These results indicate that SAEC-H7
contain a functional molecular clock entrained by light, representing an
important tool for chronobiological and endocrinological studies in fish.
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