Molecular expression of clock genes in central and peripheral tissues of white-rumped munia (Lonchura striata)

ABSTRACT

To synchronize with the fluctuating environment, organisms have evolved an endogenous time tracking mechanism referred to as the biological clock(s). This clock machinery has been identified in almost all cells of vertebrates and categorized as central and peripheral clocks. In birds, three independent circadian clocks have been identified in the hypothalamus, the pineal and the retina which interact and generate circadian time at a functional level. However, there is a limited knowledge of molecular clockwork and integration between central and peripheral clocks in birds. Therefore, we studied the daily expression of clock genes (Bmal1, Clock, Per2, Cry1, Npas2, Rev-Erbα, E4bp4, Pparα, Hlf and Tef) in three central circadian clocks (hypothalamus, pineal and retina), other brain areas (cerebellum, optic tectum and telencephalon) and in the peripheral tissues (liver, intestine, muscle and blood) of white-rumped munia. Adult birds were exposed to equinox photoperiod (12 L:12D) for 2 weeks and were then sampled (N = 5 per time point) at six-time points (ZT1, ZT5, ZT9, ZT13, ZT17 and ZT21). Daily expressions of clock genes were studied using qPCR. We observed daily variations and tissue-specific expression patterns for clock genes. These results are consistent with the autoregulatory circadian feedback loop proposed for the mammalian system and thus suggest a conserved tissue-level circadian time generation in white-rumped munia.

KEYWORDS:

• Songbird
• hypothalamus
• pineal
• retina
• blood

Acknowledgements

Financial support to AKT via the Department of Science and Technology, New Delhi (DST/CSRI/2017/37(C) is greatly acknowledged. The authors also acknowledged the infrastructure facility supported under DST-FIST program to Department of Zoology. Junior Research Fellowship from the Council of Scientific & Industrial Research (CSIR), India (No. 09/0864(11720)/2021-EMR-1 to RL is also acknowledged.

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No potential conflict of interest was reported by the author(s).

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Funding

The author(s) reported there is no funding associated with the work featured in this article.