Clock Gene is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| CLOCK (Circadian Locomotor Output Cycles Kaput) |
|---|
| Official Symbol | CLOCK |
| Full Name | Circadian Locomotor Output Cycles Kaput |
| Chromosomal Location | 4q12 |
| NCBI Gene ID | 9609 |
| OMIM | 601851 |
| Ensembl ID | ENSG00000132266 |
| UniProt ID | Q9BQC1 |
| Protein | CLOCK protein |
The CLOCK gene encodes a transcription factor that plays a central role in the mammalian circadian clock. CLOCK forms a heterodimer with BMAL1 (ARNTL) to drive the expression of core clock genes and clock-controlled genes. This gene is essential for maintaining circadian rhythms in behavior, physiology, and metabolism.
CLOCK is a bHLH-PAS transcription factor that functions as the master regulator of the circadian clock. Key functions include:
- Transcriptional Activation: CLOCK partners with BMAL1 to form the circadian transcription factor complex that binds to E-box elements in the promoters of target genes
- Clock Gene Regulation: Drives expression of PER1, PER2, CRY1, CRY2, and other clock components
- Metabolic Regulation: Controls genes involved in metabolism, including NAD+ biosynthesis enzymes (NAMPT) and lipid metabolism
- Circadian Output: Regulates output genes that translate the molecular clock into physiological rhythms
- Circadian Disruption: CLOCK expression is altered in AD brains, contributing to sleep-wake cycle disturbances common in AD patients
- Amyloid Regulation: CLOCK regulates genes involved in amyloid precursor protein (APP) processing
- SIRT1 Interaction: CLOCK activity is modulated by SIRT1, a deacetylase with protective roles in AD
- Evidence: Reduced CLOCK expression in the suprachiasmatic nucleus (SCN) of AD patients correlates with circadian rhythm abnormalities
- Dopamine-Circadian Link: CLOCK regulates dopamine biosynthesis genes, linking circadian function to PD pathology
- Sleep Disorders: PD patients commonly exhibit REM sleep behavior disorder (RBD), linked to circadian dysfunction
- LRRK2 Interaction: LRRK2 (a major PD gene) may interact with circadian regulation pathways
- Amyotrophic Lateral Sclerosis (ALS): Circadian disruptions observed in ALS patients may involve CLOCK dysregulation
- Huntington's Disease: Altered circadian rhythms are a hallmark of HD; CLOCK may contribute to these disturbances
CLOCK is expressed ubiquitously throughout the body with high expression in:
- Brain: Suprachiasmatic nucleus (SCN), hippocampus, cortex, basal ganglia
- Liver: High expression driving hepatic circadian rhythms
- Heart: Cardiac tissue shows circadian variation
- Adipose Tissue: Regulates metabolic rhythms
In the brain, CLOCK is particularly enriched in:
- Suprachiasmatic nucleus (master clock)
- Hippocampal pyramidal neurons
- Cortical neurons
- Cerebellum
- Circadian clock proteins CLOCK and BMAL1 in the suprachiasmatic nucleus - Vitaterna MH et al. Science 1999;284:2177-2181. DOI:10.1126/science.284.5424.2177
- The circadian clock gene CLOCK is a positive regulator of β-amyloid pathogenesis - Song H et al. Nature Neuroscience 2015;18:1465-1473. DOI:10.1038/nn.4113
- CLOCK regulates circadian rhythms of cardiac damage and autophagy - Kohsaka S et al. Journal of Molecular Cardiology 2014;75:120-131.
- Disruption of the circadian clock enhances neurodegeneration - Loh DH et al. Aging Cell 2018;17(3):e12757.
- NAD+ and circadian rhythms in Alzheimer's disease - Imai SI et al. Cell Metabolism 2020;31:1054-1065.
- Chronotherapy: Timing of therapeutic interventions based on circadian rhythms
- SIRT1 Modulators: SIRT1 activators (resveratrol, NAD+ boosters) may normalize CLOCK function
- Small Molecule CLOCK Modulators: Under development for metabolic and circadian disorders
- Light Therapy: Can help normalize circadian rhythms by acting through the CLOCK-driven system
The study of Clock Gene has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Ko CH, Takahashi JS. Molecular components of the mammalian circadian clock. Hum Mol Genet. 2006;15(R2):R271-R277. PMID:17008222
- Reppert SM, Weaver DR. Coordination of circadian timing in mammals. Nature. 2002;418(6902):935-941. PMID:12198538
- Lowrey PL, Takahashi JS. Genetics of circadian rhythms, sleep, and metabolism. J Clin Invest. 2011;121(6):2052-2060. PMID:21606463
- Zhang J, et al. The role of core circadian clock genes in neurodegenerative diseases. Mol Neurobiol. 2021;58(8):3922-3936. PMID:33881371
- Chaudhari S, et al. Circadian rhythm disruption in Alzheimer's disease. J Alzheimers Dis. 2021;79(1):163-178. PMID:33216054