Open image in new window Fig. 18 SIMUL8 clock properties.
We ascribed their behavior to alterations in other clock properties like amplitude [13].
We have shown previously that for individuals of extreme chronotype ("larks" and "owls"), clock properties measured in human fibroblasts correlated with extreme diurnal behavior.
In each trial, the correlations that we observed suggested that this easy cellular method could be used as a biomarker for human clock properties.
Interestingly, although blind individuals showed on average the same fibroblast clock properties as sighted ones, their physiological periods were significantly longer.
We conclude that the period of human circadian behaviour is mostly driven by cellular clock properties in normal individuals and can be approximated by measurement in peripheral cells such as fibroblasts.
In the five studies from three laboratories that we have analyzed, we have observed good correlations between period lengths of the circadian oscillator in vivo and in vitro, even among individuals whose clock properties vary very little (Figure 2).
The spatial convergence of PDF and CRY signaling at critical pacemaker nodes may create a coincidence detector, whose super-additive read-out(s) could alter clock properties more efficiently than either one alone.
We therefore asked if Shaw-mediated electrical silencing would affect molecular clock properties in the whole fly heads (largely reflecting clock gene expression in the compound-eye photoreceptor cells) and determined the abundance and phosphorylation state of endogenous PER (e.g., [32]).
Probably because of these mechanistic similarities, our laboratory has been able to show previously that clock properties of fibroblasts taken from subjects of extreme chronotype (i.e. "larks" and "owls") generally correlate with the results of questionnaires about subject daily behavior.
