From light to genes: moving the hands of the circadian clock.
Mammalian circadian rhythms are generated by the hypothalamic suprachiasmatic nuclei and finely tuned to environmental periodicities by neurochemical responses to the light-dark cycle. Light reaches the clock through a direct retinohypothalamic tract, primarily through glutamatergic innervation, and its action is probably regulated by a variety of other neurotransmitters. A key second messenger in circadian photic entrainment is calcium, mobilized through membrane channels or intracellular reservoirs, which triggers the activation of several enzymes, including a calcium/calmodulin-dependent protein kinase and nitric oxide synthase. Other enzymes activated by light are mitogen-activated- and cGMP-dependent protein kinase; all of the above have been reported to be involved in the circadian responses to nocturnal light pulses. These mechanisms lead to expression of specific clock genes which eventually set the phase of the clock and of clock-controlled circadian rhythms.
Golombek
Diego A
DA
Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Buenos Aires, Argentina. dgolombek@unq.edu.ar
Ferreyra
Gabriela A
GA
Agostino
Patricia V
PV
Murad
Alejandro D
AD
Rubio
María F
MF
Pizzio
Gastón A
GA
Katz
Marcelo E
ME
Marpegan
Luciano
L
Bekinschtein
Tristán A
TA
D000818:Animals; D001683:Biological Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D005796:Genes / Q000502:physiology*; D006801:Humans; D008027:Light