The monarch butterfly clock affords unique opportunities to further our knowledge of circadian clock mechanisms in animals. In terms of fundamental brain mechanisms, the circadian system is among the most tractable models for understanding the cellular and molecular events connecting genes to behavior. Dissecting the genetic basis of circadian behavior may help us decipher this connection for more complex behaviors.
There are also vital biomedical implications to a more thorough grasp of how the circadian clocks work. The importance of circadian rhythms in human biology is now clearly recognized. Temporal variations in hormone levels, pharmacokinetics, and disease processes (e.g., the increased incidence of heart attacks in the early morning) reveal the prominent influence of the circadian clock on human physiology and pathophysiology. Understanding the molecular clock has already helped reveal how clock gene mutations contribute to disorders of the timing of sleep, and could illuminate how clock gene mutations contribute to diseases like major depression and seasonal affective disorder. Such understanding should also lead to new pharmacological strategies for manipulating the human clock to help treat jet lag, shift-work ailments, and clock-related sleep and psychiatric disorders.
The monarch butterfly has also inspired our research into animal magnetoreception, focused on geomagnetic perception by light-sensitive chemical reactions involving the flavoprotein cryptochrome (CRY). As an extension of our butterfly work, we have recently shown, using a transgenic approach, that human CRY2, which is heavily expressed in the retina, can function as a magnetosensor in the magnetoreceptive system of Drosophila and that it does so in a light-dependent way. The finding that human CRY2 has the molecular capability to function as a light-sensitive magnetosensor has reopened an area of sensory biology that is ready for further exploration in humans. We have suggested that future research of human magnetosensitivity should focus on the influence of magnetic fields on visual function, rather than non-visual navigation.