Circadian clocks tell our body when to sleep, eat, and wake, while separate developmental clocks control the timing of growth and cell differentiation. Traditionally, these two types of biological timers have been studied separately. Now, a collaboration between the Grosshans lab at the FMI and the Partch and Ward labs at the University of California-Santa Cruz shows that they may share a fundamental molecular machinery.

The discovery centers on LIN-42, a protein in the tiny worm C. elegans that is closely related to the mammalian PER protein, a key component of the circadian clock. While PER tracks daily cycles, LIN-42 orchestrates the worm’s developmental, putting events such as molting on a regular schedule. LIN-42 partners with and gets modified by another protein, KIN-20 — similarly to how PER gets modified by the CK1 protein in mammals. If these interactions are broken, molting schedules become irregular, as do circadian rhythms.

But the work shows that LIN-42 does more than just get modified by KIN-20, it also helps control where KIN-20 is in the cell and how active it is, keeping developmental —and likely circadian — rhythms on track.

By connecting circadian and developmental timing, the findings offer a new perspective on how organisms measure time in different biological contexts, says study co-author Helge Grosshans. “Our work shows how conserved molecular machinery can be repurposed to control both daily rhythms and developmental times,” he says. “Yet not all of the machinery is conserved — so what makes the conserved parts special, and what benefits come from the unique ones? That’s our next question.”