Live imaging of altered period1 expression in the suprachiasmatic nuclei of Vipr2⁻/⁻ mice

• Published in: Journal of neurochemistry 2008-08, Vol.106 (4), p.1646-1657
• Main Authors: Hughes, Alun T.L, Guilding, Clare, Lennox, Laura, Samuels, Rayna E, McMahon, Douglas G, Piggins, Hugh D
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cells, Cultured; Chronobiology; circadian; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Eye Proteins - analysis; Eye Proteins - biosynthesis; Eye Proteins - genetics; Female; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - physiology; green fluorescent protein; image analysis; Male; Medical sciences; Mice; Mice, Knockout; Mice, Transgenic; Microscopy, Confocal - methods; Motor Activity - physiology; Neurology; Period Circadian Proteins; period1; Receptors, Vasoactive Intestinal Peptide, Type II - analysis; Receptors, Vasoactive Intestinal Peptide, Type II - biosynthesis; Receptors, Vasoactive Intestinal Peptide, Type II - deficiency; Receptors, Vasoactive Intestinal Peptide, Type II - genetics; Receptors, Vasoactive Intestinal Peptide, Type II - physiology; suprachiasmatic nucleus; Suprachiasmatic Nucleus - chemistry; Suprachiasmatic Nucleus - metabolism; vasoactive intestinal peptide; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2008.05520.x

Vasoactive intestinal polypeptide and its receptor, VPAC₂, play important roles in the functioning of the brain's circadian clock in the suprachiasmatic nuclei (SCN). Mice lacking VPAC₂ receptors (Vipr2⁻/⁻) show altered circadian rhythms in locomotor behavior, neuronal firing rate, and clock gene expression, however, the nature of molecular oscillations in individual cells is unclear. Here, we used real-time confocal imaging of a destabilized green fluorescent protein (GFP) reporter to track the expression of the core clock gene Per1 in live SCN-containing brain slices from wild-type (WT) and Vipr2⁻/⁻ mice. Rhythms in Per1-driven GFP were detected in WT and Vipr2⁻/⁻ cells, though a significantly lower number and proportion of cells in Vipr2⁻/⁻ slices expressed detectable rhythms. Further, Vipr2⁻/⁻ cells expressed significantly lower amplitude oscillations than WT cells. Within each slice, the phases of WT cells were synchronized whereas cells in Vipr2⁻/⁻ slices were poorly synchronized. Most GFP-expressing cells, from both genotypes, expressed neither vasopressin nor vasoactive intestinal polypeptide. Pharmacological blockade of VPAC₂ receptors in WT SCN slices partially mimicked the Vipr2⁻/⁻ phenotype. These data demonstrate that intercellular communication via the VPAC₂ receptor is important for SCN neurons to sustain robust, synchronous oscillations in clock gene expression.