Deletion of Clock Gene Period1 (Per1) in Neurons but Not in Astrocytes Shortens Clock Period and Diminishes Light-Mediated Rapid Phase Advances in Mice

The circadian clock enables organisms to anticipate daily recurring events and synchronize their internal rhythms with environmental cues, such as light, aligning with the day/night cycle. Central to the molecular mechanisms of the circadian clock and light sensing are the <i>Period</i> (<i>Per</i>) 1 and 2 genes. While the roles of <i>Per2</i> in astrocytes and neurons have been characterized, the specific contributions of <i>Per1</i> remain less understood. Previous research has shown that <i>Per2</i> in neurons, but not astrocytes, influences phase shifts, whereas the regulation of the circadian period involves <i>Per2</i> in both cell types. In this study, we investigated the role of <i>Per1</i> in neurons and astrocytes in modulating the circadian period and phase shifts. Using an Aschoff Type I protocol (constant darkness) combined with 15 min light pulses at circadian times (CT) 10, 14, and 22, we found that the absence of <i>Per1</i> in neurons-but not in astrocytes-significantly affected both the circadian period and phase advance shifts in response to light at CT22.