Longitudinal Tracking Reveals Developmental Transitions in Zebrafish Clock Gene Expression.

Distinct temporal frames of circadian gene expression were identified during zebrafish development.

• Two stages of circadian gene expression were observed: an embryonic stage and a larval stage.
• The genes exhibited different patterns of regulation; one showed early rhythmic expression independent of light signals but required activity.
• The other gene displayed light-responsive transcription while remaining largely independent of activity.
• Both genes had endogenous expression during the embryonic stage that was not solely driven by light, suggesting developmental inputs are significant.
• These findings indicate that zebrafish circadian gene regulation involves gene-specific programs rather than a unified activation process.

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