Fig. 4.

Effect of sleep restriction on the phase of circadian genes. (A) Genes with a prevalent circadian variation during the constant routine/total sleep deprivation after the control condition (2,103 probes that target 1,855 genes, FDR <5%). Heatmap rows correspond to the median of the melatonin-aligned probe values across all participants in the control condition. Rows are clustered based on a circular self-organizing map. Cluster means are plotted above as time-series and the number of genes per cluster (C1–C5) is indicated in parenthesis (genes belonging to multiple clusters are counted in each cluster independently). Color codes to the left of the heatmap correspond to the colors of the clusters. Sampling times and melatonin profile shown correspond to the average values across all participants in the control condition. Genes related to circadian rhythmicity and sleep (according to Gene Ontology) are indicated in the heatmap (colors indicate cluster location). (B) Phase histogram of melatonin-aligned peak times of prevalent circadian genes following control (black contour; 2,103 probes circadian in an average of 11.56 participants, n = 24,311) and sleep restriction (red contour; 1,644 probes circadian in an average of 10.50 participants, n = 17,276). The distribution of the phases is significantly different between conditions (on 1-h binned data, χ² = 1305.785, df = 23, P < 2.2 × 10⁻¹⁶). Histogram bins are 1-h-wide and bin heights are normalized to the maximum bin height per variable. The relative clock times and melatonin profile shown correspond to the average values across all participants and sleep conditions. (C) The top 10 enriched Gene Ontology Biological Processes and Molecular Functions within the circadian gene list of the control condition as identified by WebGestalt when using the human genome as a background (62). Percentages are based on the number of unique gene symbols annotated as belonging to a specific biological process/molecular function compared with the number of unique gene symbols within the entire gene list. Color bars indicate the enrichment of a process/function, where red is the most enriched (top process/function) and yellow the least enriched (number 10 of the top 10). P values are the Benjamini and Hochberg (18) -corrected P values as calculated by WebGestalt (62).