You'll have to pee at least once during an 8-hour workday. So how can most of us sleep through the night without visiting the porcelain throne? New research fingers the circadian clock, a molecular timer responsible for keeping us on daily sleep-wake cycles. Scientists compared urination patterns, both volume and frequency, in normal mice and in mice genetically engineered without two circadian genes, Cryptochrome-1 and Cryptochrome-2, resulting in dysfunctional circadian rhythms. They found that a circadian gene called Rev-erbα controlled the production of Cx43, a protein that determines how much urine bladders hold. Normal mice urinated more frequently when awake, compared with when they slept, while genetically altered mice urinated without regard to daily cycles, scientists report online today in Nature Communications. (Normal and engineered mice produced the same volume of urine.) The researchers also found that increases in Rev-erbα caused increases in Cx43 concentrations when normal mice were awake. Since more Cx43 means less room in the bladder, the team speculates that although normal mice didn't stop producing urine when asleep, their bladders were able to hold more due to decreased Cx43 concentrations. This allowed the mice to urinate less frequently. The authors note that scientists investigating why children wet the bed or why older people get up to urinate during the night should consider circadian clock effects.
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