University of Windsor graduate Kathyani Parasram (PhD 2023) has discovered how biological timing is born in fruit flies, shedding light on when circadian rhythms turn on in animals and providing a path for future research in other species.

The circadian rhythm is a molecular timekeeper that runs on a 24-hour cycle, present from cyanobacteria to mammals. Best known from sleep-wake cycles, humans in fact have daily rhythms in feeding-fasting, heartbeat and blood pressure, immune system activity, metabolism, the release of hormones, and indeed most of the functions of the organs in our bodies.

“Circadian rhythms are evolutionarily conserved in all animals, and they are present in nearly all cells in the body due to a genetic timer called the circadian clock,” says Dr. Parasram.

“For many years, researchers have asked when during development circadian timing starts – we know for instance that in newborn babies, circadian rhythms are absent for many months, keeping parents awake at all hours for the first year. Most of past work has been focused on the brain and behaviours.”

But how does a clock emerge in the cells of the body? To answer this question, Parasram looked at the clock of a simple animal: Drosophila melanogaster, the common fruit fly. This animal is a favorite in research because – even though it looks quite different – the cells in the fly are evolutionarily related to those in all animals.

“Using single cell sequencing and Drosophila genetics, we determined that the circadian clock is completely absent during most of the life cycle stages of the fly,” says Parasram.

“The genes that control circadian rhythms do not get turned on until the insect hatches from its pupal case as an adult. In response to hormones released as the insect hatches the clock turns on quickly, and then the environment synchronizes the clocks in the cells to match day-night cycles.”

Her research was done in Phillip Karpowicz’s lab in the Department of Biomedical Sciences and recently published in the journal Nature Communications. Collaborators from Brian Deveale’s UWindsor lab and Edan Foley’s lab at the University of Alberta were co-authors.

This work shows that circadian rhythms in the body of insects, the most abundant type of animal on Earth, are born surprisingly late during adulthood, with implications for everything from insect ecology to pest control.