Dissociation of circadian activity and singing behavior from gene expression rhythms in the hypothalamus, song control nuclei and cerebellum in diurnal zebra finches

Jul 13, 2019Chronobiology international

Daily activity and singing behavior are separate from gene expression rhythms in brain areas controlling song and movement in daytime zebra finches

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Abstract

Daily rhythms in singing and activity were maintained in 70% of male zebra finches raised under constant light conditions.

Circadian functions typically remain closely linked, but this may not hold true for birds under certain light conditions.
In constant light, 30% of zebra finches displayed arrhythmic behavior in singing and activity.
Daily rhythms in clock gene expression were observed in key brain regions under light-dark conditions, but rhythmicity was lost in constant light.
The overall quality of song decreased under constant light conditions.
This study suggests a dissociation between circadian behavior and genetic oscillations in response to light environments.

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Under periodic day-night environment, most circadian functions maintain a close phase relationship relative to each other, suggesting a common circadian pacemaker control of different overt rhythms. In birds, this seems highly unlikely, given multioscillatory nature of the circadian pacemaker and downstream generation of several circadian behaviors. We hypothesized the dissociation of overt rhythms from circadian gene oscillations, if the two were loosely coupled, under an aperiodic light condition. We tested this in daily rhythms in singing, activity and clock gene expressions in adult male zebra finches () that were born and raised under the constant light (LL; 24L:0D), with controls on an LD cycle (12L: 12D). Particularly, we monitored daily pattern of singing and activity behavior, and measured 24 h mRNA expression of immediate early gene (), clock genes (and) and epigenetic marker genes (and) in the hypothalamus, and of clock genes and genes coding for the aromatase (), androgen receptor () and dopamine receptor () in the song control nuclei (Area X and HVC) and cerebellum (motor control region). We found persistence of daily rhythms in activity and singing in all birds under LD, but in only 70% (14/20) birds under LL; thus, both behaviors were arrhythmic in 30% (6/20) birds) under LL. The overall song quality was also declined under LL. The clock genes showed daily rhythms in the hypothalamus, song control nuclei (exceptin Area X) and cerebellum under LD, although with differences in peak expression times; however, there was loss of rhythmicity in clock genes (exceptin Area X and HVC) under LL. We also found dailymRNA rhythm in the Area X and cerebellum under LD. These results demonstrate for the first time the persistence of clock gene oscillations in the song control brain regions and show the dissociation of circadian behavior from genetic oscillations in relation to an imposed light environment. Taeniopygia guttata c-Fos Bmal1, Per2Rev-erb β Dnmt3b Tet2Arom Ar Drd2Per2Bmal1Ar

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Dissociation of circadian activity and singing behavior from gene expression rhythms in the hypothalamus, song control nuclei and cerebellum in diurnal zebra finches

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