Sleep Genes are not the same as ‘Genes for sleep’

Back in the late 1990s, when people first started using various differential screens, etc. looking for elusive “genes for sleep”, I wrote in my written prelims (and reprinted it on my blog several years later):

Now the sleep researchers are jumping on the bandwagon of molecular techniques. They are screening for differences in gene expression between sleeping and awake humans (or rats or mice), searching quite openly for the “genes for sleep”. Every time they “fish out” a gene, it turns out to be Protein kinase A, a dopamine receptor, or something similar with a general function in the brain. Don’t they understand that sleep (like hibernation) is an emergent property of a multicellular brain? Unlike in the clock field, a single neuron does not carry the function – it does not sleep. Only whole (or halves of) brains can be asleep or awake. The sleep “mechanism” is not a molecular mechanism but a result of a particular pattern of neural connectivity and activity.

And, lo an behold, all the genes that affect sleep (the duration or quality of it, not timing which is guided by the circadian clock), turned out to be those “maintanance” molecules, involved in general, day-to-day activity of neurons. Most geneticists have since moved away from such a simplistic, bean-bag genetics notion of sleep and started studying sleep from a much more integrative perspective. But some persist. The newest discovery of a “sleep-gene” is just like what I predicted, a general-maintanance molecule – an ion channel:
Second Sleep Gene Identified:

A gene that controls the flow of potassium into cells is required to maintain normal sleep in fruit flies, according to researchers at the University of Wisconsin School of Medicine and Public Health (SMPH). Hyperkinetic (Hk) is the second gene identified by the SMPH group to have a profound effect on sleep in flies.
The finding supports growing evidence that potassium channels–found in humans and fruit flies alike–play a critical role in generating sleep.
“Without potassium channels, you don’t get slow waves, the oscillations shown by groups of neurons across the brain that are the hallmark of deep sleep,” says Chiara Cirelli, SMPH psychiatry professor and senior author on the latest study, which appeared in the May 16, 2007, Journal of Neuroscience.

Very cool and important for the advancement of our understanding of sleep, but surely not a “gene for sleep”.


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