Circadian clocks in the mammalian brain

Area of Science:

• Chronobiology
• Molecular Biology
• Neuroscience

Background:

• Multicellular organisms exhibit daily physiological and behavioral cycles driven by endogenous circadian clocks.
• In mammals, the suprachiasmatic nuclei (SCN) in the hypothalamus houses the central circadian clock, regulating activity, neuroendocrine, and autonomic functions.
• The retina also contains intrinsic circadian oscillators.

Purpose of the Study:

• To investigate the molecular basis of the mammalian circadian clock.
• To characterize the roles of newly identified mammalian "clock genes," homologous to Drosophila melanogaster genes, within the SCN.
• To understand how cellular circadian signals coordinate physiological and behavioral rhythms across the entire neuraxis.

Main Methods:

• Identification of mammalian homologues of Drosophila circadian clock genes.
• Analysis of the molecular mechanisms underlying circadian gene expression in the SCN.
• Investigation of the functional roles of these genes in the SCN's clockwork.

Main Results:

• Mammalian homologues of Drosophila clock genes have been identified.
• These genes are integral to a cell-autonomous, genetically determined mechanism within the SCN.
• The identified genes likely participate in a negative feedback loop, similar to Drosophila, to establish circadian gene expression cycles.

Conclusions:

• The molecular machinery of the mammalian circadian clock involves specific "clock genes" that regulate gene expression in a cyclical manner.
• Understanding these genes' functions in the SCN is crucial for comprehending the molecular basis of behavior and circadian rhythm regulation.
• Further characterization will elucidate how the SCN imposes temporal order on the organism's physiology and behavior.