Suprachiasmatic function in a circadian period mutant: Duper alters light‐induced activation of vasoactive intestinal peptide cells and PERIOD1 immunostaining

Abstract

Mammalian circadian rhythms are entrained by photic stimuli that are relayed by retinal projections to the core of the suprachiasmatic nucleus (SCN). Neuronal activation, as evidenced by expression of the immediate early gene c-fos, leads to transcription of the core clock gene per1. The duper mutation in hamsters shortens circadian period and amplifies light-induced phase shifts. We performed two experiments to compare the number of c-FOS immunoreactive (ir) and PER1-ir cells, and the intensity of staining, in the SCN of wild type (WT) and duper hamsters at various intervals after presentation of a 15-minute light pulse in the early subjective night. Light induced c-FOS-ir within 1h in the dorsocaudal SCN of duper, but not WT hamsters. In cells that express vasoactive intestinal peptide (VIP), which plays a critical role in synchronization of SCN cellular oscillators, light-induced c-FOS-ir was greater in duper than WT hamsters. After the light pulse, PER1-ir cells were found in more medial portions of the SCN than FOS-ir, and appeared with a longer latency and over a longer time course, in VIP cells of duper than wild type hamsters. Our results indicate that the duper allele alters SCN function in ways that may contribute to changes in free running period and phase resetting.

The duper mutation reveals previously unsuspected functions of Cryptochrome 1 in circadian entrainment and heart disease

“…Cry1 deficiency may act in vasoactive intestinal peptide (VIP) cells to alter coupling but in arginine vasopressin (AVP) cells to affect circadian output. Light-induced activation and Per1 expression in the VIP cell population is altered in duper ( 58 ). Deletion of VIP in mice weakens coupling, ultimately resulting in arrhythmicity, but changes in period and acceleration of phase shifts are inconsistent and do not match the duper phenotype ( 51 ).…”

Neuroendocrine effects of the duper mutation in Syrian hamsters: a role for Cryptochrome 1

“…Crypoprotected sections were rinsed in PBS and blocked as previously described ( Manoogian et al, 2018 ). Preoptic sections were stained using rabbit anti-GnRH (1:2,500; LR-1, a generous gift of Robert Benoit), goat anti-Per1 (1:200, Bethyl) and guinea pig anti-Bmal1 (1:20,000, a gift of David R. Weaver; LeSauter et al, 2012 ).…”

duperis a null mutation of Cryptochrome 1 in Syrian hamsters

“…Before mounting, sections were incubated in Neurotrace FluroNissl 500/525 for 30 min (ThermoFisher, N21480, 1:300). Immunostaining was assessed using a Zeiss 700 confocal microscope as previously described ( 55 ).…”