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Circadian Responses to Light in the BTBR Mouse
Jhenkruthi Vijaya Shankara1,2, Katelyn G Horsley1,2, Ning Cheng3,4
1Department of Psychology, University of Calgary, Calgary, AB, Canada.
Journal of Biological Rhythms
|June 20, 2022
Summary
BTBR mice, a model for autism spectrum disorders (ASD), exhibit short circadian rhythms and altered light responses. These findings offer insights into circadian clock mechanisms and sleep disruptions in ASD.
Area of Science:
- Chronobiology
- Neuroscience
- Animal Models
Background:
- Circadian rhythms are crucial for physiological processes, and disruptions are linked to various clinical conditions.
- Autism spectrum disorder (ASD) is frequently associated with significant sleep and circadian rhythm abnormalities.
- BTBR T+Itpr3tf/J (BTBR) mice are a relevant model for studying ASD due to observed sleep disturbances.
Purpose of the Study:
- To investigate the circadian phenotype of BTBR mice under freerunning and light-entrained conditions.
- To compare the circadian properties of BTBR mice with C57BL/6J control mice.
- To explore the relationship between circadian parameters and the suprachiasmatic nucleus (SCN) in BTBR mice.
Main Methods:
- Assessment of circadian freerunning periods and activity levels in BTBR and control mice.
- Evaluation of responses to light-dark cycles, including phase advances and delays.
- Analysis of entrainment to standard and skeleton photoperiods.
- Correlation of circadian period differences with vasoactive intestinal polypeptide (VIP) cell counts in the SCN.
Main Results:
- BTBR mice displayed significantly shorter freerunning periods (~22.75 h) compared to controls.
- BTBR mice exhibited increased activity levels compressed into a shorter active phase.
- BTBR mice showed larger phase shifts in response to light and accelerated entrainment to altered light cycles.
- Entrainment to minimal light exposure (1-min photoperiods) suggests robust circadian regulation independent of masking effects.
- Differences in circadian period correlated with variations in VIP-expressing cell numbers in the SCN.
Conclusions:
- BTBR mice possess distinct circadian properties, including a short endogenous period and enhanced light responsiveness.
- Despite their altered circadian phenotype, BTBR mice demonstrate normal and accelerated entrainment capabilities.
- The BTBR mouse model offers a valuable platform for investigating the genetic and neural underpinnings of circadian clock function and its relevance to ASD.
Keywords:
VIPautism spectrum disordersentrainmentfreerunning periodmaskingmousephase shiftsuprachiasmatic nucleusMore Related Videos
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