Understanding the circadian system as a net of clocks: daily expression of clock genes in the hypothalamus-pituitary-interrenal axis in Carassius auratus

In the last years, the HPI axis has been suggested as a candidate to harbour peripheral oscillators in mammals. To investigate this issue in fish, we analysed the daily expression of clock genes along the HPI axis in goldfish (Carassius auratus) maintained under 12L:12D photoperiod, and scheduled fed daily during 4 weeks. Goldfish were sampled every 3 hours during a whole 24-h cycle. Hypothalamus, pituitary and head kidney were extracted to quantify the transcription of clock genes (per1a, per2a, per3, cry1a, cry2a, cry3, clock1a y bmal1a) and genes related with the activation of the HPI axis: crh precursor in hypothalamus, crh-r1 and pomc in pituitary, and mc2r and star in head kidney. All the tissues analysed showed a daily rhythm of expression of per1a, per3, cry3 and clock1a, with acrophases at the dark-light transition for per1a, per3 and cry3, and in the light-dark transition for clock1a. These profiles resembled the ones in central structures of goldfish and zebrafish. Except for crh-r1, no significant daily rhythmic expression was found for any of the HPI axis genes studied, although a rhythmic regulation at other non-transcriptional levels cannot be discarded. These results suggest for the first time in fish the existence of a functional clock within the HPI axis.

Autor: 
Azpeleta C., Sánchez-Bretaño A., Isorna E., Nisembaum L.G., Velarde E., De Pedro N., Alonso-Gómez A.L. y Delgado M.J.
Referencia: 
Avances en Endocrinología Comparada
Volumen: 
VI
Pagina Inicial: 
37
Pagina final: 
40