Email updates

Keep up to date with the latest news and content from JCR and BioMed Central.

Open Access Research

Investigation of a non-invasive method of assessing the equine circadian clock using hair follicle cells

Lisa M Watts, John A Browne and Barbara A Murphy*

Author Affiliations

School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland

For all author emails, please log on.

Journal of Circadian Rhythms 2012, 10:7  doi:10.1186/1740-3391-10-7

Published: 5 October 2012



A comprehensive understanding of the equine circadian clock involves the evaluation of circadian clock gene expression. A non-invasive and effective method for detecting equine clock gene expression has yet to be established. Currently, research surrounding this area has relied on collecting tissue biopsies or blood samples that can often be costly, time consuming and uncomfortable for the animal.


Five mares were individually stabled under a light–dark (LD) cycle that mimicked the external environmental photoperiod during a time of year corresponding with the vernal equinox. Hair follicles were collected every 4 h over a 24-h period by plucking hairs from the mane. RNA was extracted and quantitative (q) PCR assays were performed to determine temporal expression patterns for the core clock genes; ARNTL, CRY1, PER1, PER2, NR1D2 and the clock controlled gene, DBP.


Repeated measures ANOVA for the clock gene transcripts PER1 and PER2 and the clock controlled gene, DBP, revealed significant variation in expression over time (p < .05, respectively). Cosinor analysis confirmed a significant 24-h temporal component for PER1 (p = .002) and DBP (p = .0033) and also detected rhythmicity for NR1D2 (p = .0331).


We show that the extraction of RNA from equine hair follicle cells can identify the circadian 24 h oscillations of specific clock genes and a clock-controlled gene and therefore provide a valuable non-invasive method for evaluating the equine peripheral circadian clock. This method will serve as a useful tool for future evaluations of equine circadian rhythms and their response to environmental changes.

Equine; Horse; Clock; qPCR; Hair follicle; PER1; PER2; DBP; NR1D1; Circadian