标题:CHRONO and DEC1/DEC2 compensate for lack of CRY1/CRY2 in expression of coherent circadian rhythm but not in generation of circadian oscillation in the neonatal mouse SCN
摘要:Clock genes
Cry1 and
Cry2, inhibitory components of core molecular feedback loop, are regarded as critical molecules for the circadian rhythm generation in mammals. A double knockout of
Cry1 and
Cry2 abolishes the circadian behavioral rhythm in adult mice under constant darkness. However, robust circadian rhythms in PER2::LUC expression are detected in the cultured suprachiasmatic nucleus (SCN) of
Cry1/
Cry2 deficient neonatal mice and restored in adult SCN by co-culture with wild-type neonatal SCN. These findings led us to postulate the compensatory molecule(s) for
Cry1/Cry2 deficiency in circadian rhythm generation. We examined the roles of
Chrono and
Dec1/Dec2 proteins, the suppressors of
Per(s) transcription similar to CRY(s). Unexpectedly, knockout of
Chrono or
Dec1/
Dec2 in the
Cry1/
Cry2 deficient mice did not abolish but decoupled the coherent circadian rhythm into three different periodicities or significantly shortened the circadian period in neonatal SCN. DNA microarray analysis for the SCN of
Cry1/
Cry2 deficient mice revealed substantial increases in
Per(s),
Chrono and
Dec(s) expression, indicating disinhibition of the transactivation by BMAL1/CLOCK. Here, we conclude that
Chrono and
Dec1/
Dec2 do not compensate for absence of CRY1/CRY2 in the circadian rhythm generation but contribute to the coherent circadian rhythm expression in the neonatal mouse SCN most likely through integration of cellular circadian rhythms.