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Non-photic phase resetting of Dexras1 deficient mice: a more complicated story
1Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA, USA. robert@dallmanns.de
Abstract:
Recently, it has been reported that mice deficient for Dexras1 have a diminished phase-shifting response to photic stimuli but an enhanced response to non-photic stimuli; the latter is of additional interest in that mice generally show relatively weak and unreliable responses to non-photic events. Therefore, in situations in which both photic and non-photic stimuli are present, control of circadian rhythms, relative to wild-types, should tip toward non-photic stimuli in Dexras1(-/-) mice. However, we detected no differences in an experiment in which photic and non-photic entraining agents were presented 180 degrees out of phase, i.e. were in conflict with each other. Furthermore, Dexras1(-/-) and wild-type mice did not differ in non-photic phase shifting to a pulse of confinement in a novel running wheel. Suppression of locomotion by light (masking effect) did not differ between the genotypes, indicating that the photoreceptor input to the non-image forming system is intact. The circadian phenotype of Dexras1(-/-) mice appears to be more complicated than previously thought.
Insights
Mice lacking Dexras1 show altered responses to light and non-light cues affecting circadian rhythms. Their complex circadian phenotype suggests further investigation into Dexras1
Area of Science:
- Chronobiology
- Molecular Biology
- Genetics
Background:
- Dexras1 deficiency in mice reportedly alters circadian rhythm responses to photic and non-photic stimuli.
- Mice typically exhibit weak responses to non-photic circadian entrainment cues.
- Dexras1(-/-) mice were hypothesized to show a stronger reliance on non-photic stimuli for circadian regulation.
Purpose of the Study:
- To investigate the circadian rhythm phenotype of Dexras1(-/-) mice.
- To determine if Dexras1 deficiency alters the balance between photic and non-photic circadian entrainment.
- To assess the functional integrity of the non-image forming visual system in Dexras1(-/-) mice.
Main Methods:
- Comparative analysis of circadian rhythm phase shifting in Dexras1(-/-) and wild-type mice.
- Exposure to conflicting photic and non-photic entraining stimuli.
- Assessment of non-photic phase shifting using a novel running wheel confinement paradigm.
- Measurement of light-induced suppression of locomotion (masking effect).
Main Results:
- No significant differences were observed between Dexras1(-/-) and wild-type mice when exposed to conflicting photic and non-photic entraining stimuli.
- Dexras1(-/-) mice did not exhibit altered non-photic phase shifting in response to running wheel confinement.
- Light-induced masking effects were comparable between genotypes, indicating intact photoreceptor input.
Conclusions:
- The circadian phenotype of Dexras1(-/-) mice is more complex than initially suggested by previous reports.
- Dexras1 does not appear to be essential for balancing photic and non-photic circadian entrainment in mice.
- The non-image forming visual system's response to light is functional in Dexras1-deficient mice.
