Project 8.3

Adaptation to daily reoccurring events takes place in almost all organisms and is made possible by the presence of transcription-translation feedback loops that allow for oscillating expression of genes with a ~24 hour periodicity. Like most insects, Anopheles gambiae contains an ancestral clock-setup, differentiating itself from the one found in mammals in the repressive phase of the feedback loop. We aim to understand how circadian regulation works from a mechanistic standpoint.

Circadian clocks are molecular regulators that exist in almost all living beings and allow anticipation and adaptation to daily reoccurring events. They have developed several times in plants, animals and cyanobacteria, and regulate a multitude of cellular and behavioural processes.

Mammalian clocks are made up of a transcription-translation feedback loop, where the activators CLOCK and BMAL1 induce the expression of so-called clock-controlled genes (CCGs), including those for CRYPTOCHROME (CRY) 1/2 and PERIOD (PER) 1/2/3. CRY and PER proteins translocate into the nucleus, where act as potent repressors of CLOCK/BMAL1 mediated transcriptional activation, repressing their own expression which generates oscillating expression of CCGs.

While the core feedback loop in insects is similar to the one found in mammals, most insects only possess one PER-protein and one repressor-type-CRY. Some additionally express a photosensitive CRYPTOCHROME that serves as a blue-light receptor, and TIMELESS, a component of the core oscillator in Drosophila melanogaster. The setup of circadian regulation found in these insects is considered the ancestral clock, from which the clock-architectures found in mammals or Drosophila have developed.

While a lot is known about the mammalian clock setup, knowledge about circadian rhythmicity in insects and the roles of the different elements of the ancestral clock is limited. In my project, the circadian clock in the malaria-vector Anopheles gambiae will be investigated using biochemical, biophysical and cell-based methods, and compared to the mammalian circadian clock.