Tissue clock

Laboratory support is carried out by the clinical diagnostic laboratory and laboratory of tissue typing. The equipment of clinical diagnostic laboratory allows carrying out hematological, biochemical investigations for the structural subdivisions of the Center, coagulometry, analysis of the acid-alkali state, the electrolytes of blood and several other researches in the round-the-clock mode. 

Bellingham J, Whitmore D, Philp AR, Wells DJ, Foster RG 2002 Zebrafish melanopsin isolation, tissue localisation and phylogenetic position. Mol Brain Res 107 128-136 Berson DM, Dunn FA, Takao M 2002 Phototransduction by retinal ganglion cells that set the circadian clock. Science 295 1070-1073... 

Sassone-Corsi We know that the transplanted SCN doesn t receive normal input from the retina. Is it possible that the transplanted SCN is not communicating with the rest of peripheral tissues in the same way I am not sure that the experiment of Bert van der Horst will teU us whether the transplanted SCN is able to entrain a non-functioning peripheral clock. 

Cermakian We have done almost the reverse experiments with fibroblast implants from Clock l mutants whose clock is quite impaired. When we put these fibroblast implants into mice whose SCN is functional, the SCN was not able to entrain them. So I don t think that a grafted SCN will be able to entrain peripheral tissues of these Crj double mutants. 

In mammalian tissue culture cells, robust circadian gene expression can be entrained by 12 h temperature cycles with an amplitude of 4 °C (e.g. 37 °C versus 33 °C) (Brown et al 2002). We thus wondered whether physiological temperature rhythms, themselves circadian and with an amplitude of —4 °C in most mammals, could also sustain cyclic clock-gene transcription. To this end, we engineered a... 

However, there is an apparently important difference between SCN and non-SCN rhythms in vitro-. SCN explants remain rhythmic while other regions of the brain and peripheral tissues damp after a minimum of two, but a maximum of about 15 cycles (Fig. 1). The robustness and persistence of the rhythmicity depends on the tissue and does vary in individual cultures. It has been assumed from results like these that the SCN is a self-sustained pacemaker while peripheral clocks are damped oscillators, but it cannot be excluded that in isolated peripheral tissues, I erl may damp despite the persistent rhythmicity of other clock components or that the cultures lack some factor continuously present in vivo that is required for sustained rhythmicity of non-SCN tissue. 

What is special about the testis that requires the absence of the circadian clock so pervasive in other tissues The testis has a number of characteristics, which make it quite different from other tissues. The testis contains spermatogenic cells that perform a constant and complex cell differentiation program where reductive cell divisions occur. It may be that the complex pattern of gene expression engendered by the circadian clock leads to unfavourable interactions with the developmental process of paramount importance to the testis. Alternatively, the normal oscillation of clock gene expression may be distorted by other transcriptional regulators or co-activators which are only present in seminiferous tubules (Sassone-Corsi 2002). 

Sassone-Corsi That s a good question, and we haven t done this. I would expect the effects to be from the SCN, but we need to do this experiment. I would love to see a SCN transplant in a Clock mutant mouse. But if what Bert van der Horst said in his paper (Bonnefont et al 2003, this volume) is true, that peripheral clocks are not working in Cry double knockouts where a normal SCN is introduced, this teUs me that all peripheral oscillators are not crucial for motor rhythmic activity. Could the SCN be the only thing responsible for aU the rhythmic activity I am not sure how much peripheral tissues are working in those Cry double knockouts. 

Okamura We didn t measure the clock gene expression in peripheral tissues. But there are indications that some signals were transmitted from the SCN transplant to the cortex. 

Stanewsky I would hke to return to the question of peripheral versus central oscillators. There is a difference between the lateral neuron clock and the peripheral oscillators. The only rhythm known to persist in flies is the behavioural rhythm, which is driven by the lateral neurons. Whatever other tissue you look at, per and tim expression dampens fast in constant darkness. Do you know anything about the antennal rhythms ... 

Weit You are talking about the input of your experiment when you first put them in the dish prior to serum shock. When you start there is no functioning clock in the tissue. 

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