Researchers suggest mammals have a 12-hour clock with similarities to the clock driven by the tides in sea creatures such as the crustacean E. pulchra, shown. WIKIPEDIA, HANS HILLEWAERTAlong with their standard 24-hour circadian cycle, mammals may also harbor a distinct 12-hour clock, scientists report today (June 6) in Cell Metabolism.
Researchers led by Bert O’Malley of Baylor College of Medicine in Houston, Texas, identified a set of metabolism and stress genes in mouse liver cells that followed a pattern of expression on a 12-hour cycle—starting in the morning and again in the evening. O’Malley’s team also found that a 12-hour clock, distinct from the 24-hour circadian clock, drives this morning-evening rhythm in gene expression.
The clock’s origin, the scientists suggest, may be rooted in organisms’ initial evolution in the ocean millions of years ago.
“It’s a provocative argument,” Cambridge University biologist Michael Hastings tells The Scientist in a phone interview. He’s cautious about the claim of an evolutionary connection between the 12-hour clock in sea creatures and the 12-hour cycles seen in mammals. Still, he ...
