CRYPTOCHROMES confer robustness, not rhythmicity, to circadian timekeeping

A

Representative actograms showing that CKO mice (n = 5) cannot be entrained to 8 h:8 h or 12 h:12 h light:dark cycles, whereas WT mice entrain to 12 h:12 h but not 8 h:8 h light‐dark cycles (n = 5). Equal numbers of age‐matched male and female mice were used.

B, C

For CKO mice during under LD cycles, the dominant period of behavioural rhythms is determined by the period of the zeitgeber, whereas amplitude does not vary significantly between 16‐h and 24‐h cycles. In contrast, the period of WT behavioural rhythms does not vary significantly between 16‐h and 24‐h cycles, whereas amplitude is significantly reduced under unnatural 8 h:8 h light:dark cycles. This indicates the robustness conferred by CRY to circadian rhythms of locomotor activity in WT mice in vivo. Two‐way ANOVA P‐values and significance from Sidak’s multiple comparisons test are reported; horizontal line represents mean.

D

Normalised, detrended bioluminescence recording of the XLG‐luciferase reporter (XLG‐LUC; equivalent of PER2::LUC) expressed in WT and timeless knockout (Tim^out) flies under constant darkness (detrended means ± SEM; WT n = 21, Tim^out n = 36). Note the difference in y‐axis scaling.

E

Damped sine wave fit to the data presented in (D). P‐values (extra sum‐of‐squares F‐test) indicate comparison of fit test with the null hypothesis (straight line).

F

Significant differences in the period and amplitude of XLG‐LUC rhythms of Tim^out compared with WT flies. Mean ± SEM, P‐values indicate unpaired t‐test, WT n = 21, Tim^out n = 36.

Figure EV2. Entrainment deficiency of CRY‐deficient mice to environmental light:dark cycles and Timeless‐independent protein rhythms in Drosophila melanogaster .