Photoperiod differentially regulates clock genes' expression in the suprachiasmatic nucleus of XXXX .

@entity72453 @entity72455 @entity72452 @entity72456 @entity72451 @entity72454 @entity329
The suprachiasmatic nuclei (SCN) contain the master circadian pacemaker in mammals. Generation and maintenance of circadian oscillations involve clock genes which interact to form transcriptional/translational loops and constitute the molecular basis of the clock. There is some evidence that the SCN clock can integrate variations in day length, i.e. photoperiod. However, the effects of photoperiod on clock-gene expression remain largely unknown. We here report the expression pattern of @entity72451 , @entity72452 , @entity72453 , @entity72454 , @entity72455 , @entity72456 and Clock genes in the SCN of @entity329 when kept under long (LP) and short (SP) photoperiods. Our data show that photoperiod differentially affects the expression of all clock genes studied. Among the components of the negative limb of the feedback loop, @entity72451 , @entity72452 , @entity72453 , @entity72455 but not @entity72454 genes show a shortened duration of their peak expression under SP compared with LP. Moreover, mRNA expression of @entity72451 , @entity72453 and @entity72454 are phase advanced in SP compared with LP. @entity72453 shows an mRNA peak of higher amplitude under SP conditions whereas @entity72451 and @entity72452 peak amplitudes are unaffected by photoperiod changes. @entity72456 expression is phase advanced without a change of duration in SP compared with LP. Furthermore, the expression of Clock is rhythmic under SP whereas no rhythm is observed under LP. These results, which provide further evidence that the core clock mechanisms of the SCN integrate photoperiod, are discussed in the context of the existing molecular model.
