Diurnal Preference Predicts Phase Differences in Expression of Human Peripheral Circadian Clock Genes

The 2015 study "Diurnal Preference Predicts Phase Differences in Expression of Human Peripheral Circadian Clock Genes" involved 36 individuals, 14 of whom were extreme morning or evening chronotypes. The research used a novel method of extracting RNA from human hair follicles to measure the expression of two key clock genes, Per3 and Nr1d2. The findings indicated a significant phase shift in the oscillation of these genes between morning and evening chronotypes, with an average phase difference of 2.86 hours. This suggests that an individual's diurnal preference can predict differences in the expression of their circadian clock genes. The study also found that Morningness-Eveningness Questionnaire (MEQ) scores were significantly correlated with phase differences. The research concluded that analysis of Per3 and Nr1d2 mRNA levels from hair follicle cells provides valuable markers for estimating peripheral clock oscillations in human behavioral studies.