Figure 1
Relative mRNA levels (±SE) at three sampled time points for Per3 (A) and Nr1d2 (B). Patterns of relative gene expression varied between extreme morning and evening chronotypes but were similar across the two genes. On average, there was a 2.61-hour phase difference in Per3 expression (t = 2.58, p = 0.02) and a 3.08-hour phase difference in Nr1d2 expression (t = 2.91, p = 0.01) between the two chronotypes. Combining the data predicted from both genes, there was a 2.86-hour phase difference between extreme morning and evening chronotypes (t = 2.41, p = 0.03).
Figure 2
Clock phase predicts chronotype. Age-adjusted MEQ scores (y-axis) were significantly correlated with phase differences of individuals (r = 0.75, F = 13.85, p = 0.003). Red, extreme evening chronotypes; blue, extreme morning chronotypes.
Figure 3
Relationships between wake-time and individual-specific clock phase and MEQ score. A: Average wake time in extreme chronotypes show a weak association with individual-specific phase differences (r = 0.66, F = 9.08, p = 0.011). B: Average wake times of all subjects (including non-extremes, n = 23) were correlated, as expected, with morningness-eveningness (MEQ) scores (r = 0.83, F = 46.33, p<0.001).