Related Experiment Video
Updated: Aug 9, 2026
10:38
Monitoring Cell-autonomous Circadian Clock Rhythms of Gene Expression Using Luciferase Bioluminescence Reporters
Published on: September 27, 2012
Assembling a clock for all seasons: are there M and E oscillators in the genes?
S Daan1, U Albrecht, G T van der Horst
1Zoological Laboratory, University of Groningen, Haren, The Netherlands,
Journal of Biological Rhythms
|April 17, 2001
Summary
The mammalian circadian pacemaker uses two gene complexes (per1/cry1 and per2/cry2) to track dawn and dusk, adjusting daily rhythms. This molecular model explains how the suprachiasmatic nucleus (SCN) adapts behavior to changing day lengths.
Area of Science:
- Chronobiology
- Molecular Biology
- Neuroscience
Background:
- The suprachiasmatic nucleus (SCN) acts as the mammalian circadian pacemaker.
- Circadian rhythms are regulated by molecular feedback loops involving core clock genes.
Purpose of the Study:
- To propose a molecular model for the SCN pacemaker based on a nonredundant double complex of circadian genes.
- To explain how this molecular mechanism adapts behavioral rhythms to seasonal changes in day length.
Main Methods:
- Hypothesizing a molecular composition of the SCN pacemaker.
- Describing the distinct temporal dynamics and light responses of two proposed circadian gene complexes (per1/cry1 and per2/cry2).
- Extending the E-M oscillator model to incorporate molecular components.
Main Results:
- The per1/cry1 complex (M oscillator) tracks dawn by accelerating with light and decelerating with darkness.
- The per2/cry2 complex (E oscillator) tracks dusk by decelerating with light and accelerating with darkness.
- These M and E oscillators generate distinct morning and evening components in SCN neuronal activity.
Conclusions:
- The SCN pacemaker is molecularly composed of two distinct, nonredundant circadian gene oscillators.
- This molecular mechanism enables the adaptive tuning of endogenous behavioral programs to day length in nocturnal mammals.
- The model provides specific, testable predictions for future genetic studies in circadian research.
More Related Videos
Related Concept Videos
02:45Biological Clocks and Seasonal Responses
The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
02:19Circadian Rhythms and Gene Regulation
The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
02:19Circadian Rhythms and Gene Regulation
The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
01:31Oscillations In An LC Circuit
An idealized LC circuit of zero resistance can oscillate without any source of emf by shifting the energy stored in the circuit between the electric and magnetic fields. In such an LC circuit, if the capacitor contains a charge q before the switch is closed, then all the energy of the circuit is initially stored in the electric field of the capacitor. This energy is given by
01:10Generating Electromagnetic Radiations
The German physicist Heinrich Hertz (1857–1894) was the first to generate and detect certain types of electromagnetic waves in the laboratory. Starting in 1887, he performed a series of experiments that confirmed the existence of electromagnetic waves and verified that they travel at the speed of light. Hertz used an alternating-current RLC (resistor-inductor-capacitor) circuit that resonated at a known frequency and connected it to a loop of wire. High voltages induced across the gap in the...
01:22Generation Time
Bacterial generation time, the period required for a bacterial population to double during its exponential growth phase, serves as a critical measure of microbial growth dynamics under optimal conditions. This parameter varies significantly across bacterial species and can be influenced by factors such as temperature, pH, and the availability of nutrients. For example, Escherichia coli can achieve a generation time of approximately 20 minutes, while Mycobacterium tuberculosis exhibits a much...