Time on the fly: unravelling a new circadian network in scuttle flies

• Applicant: Enrico Bertolini, Ph.D.
• Subject Area: Developmental Neurobiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465974651

Circadian clocks orchestrate physiology, metabolism and behavior in all living organisms. They are composed of core transcriptional feedback loops ticking within clock cells and leading to molecular rhythms at the level of gene expression. These rhythms are transmitted from clock cells to downstream circuits in the brain and the whole organism. To synchronize individual clock cell clusters within the brain circadian network, an evolutionarily conserved neuropeptide, Pigment-dispersing factor (PDF), is used as pacemaker signal in most insects investigated so far. Surprisingly, I found that two scuttle fly species (Diptera: Phoridae), Megaselia abdita and Megaselia scalaris, lack pdf in their genome, they do not show immunoreactivity for an arthropod conserved PDF antibody but nevertheless sustain robust circadian rhythms. This opens the exciting possibility, that these species developed a completely new circadian network communication system. In the proposed project, I want to investigate how such a novel communication system looks like and which signaling molecules compensate for the loss of PDF in Megaselia’s circadian network. First, I will generate high-quality genome assemblies for the two Megaselia species and use comparative genomics to recapitulate the evolutionary history of the pdf locus in both species. Second, I will use transgenesis and CRISPR/Cas9-mediated genome editing in M. abdita to genetically label clock neurons with transgenic markers. Thirdly, I will use these novel transgenic lines combined with single-nuclear RNA-sequencing protocols to sequence the transcriptome of all clock neurons in M. abdita. By comparing the clock transcriptome of M. abdita with that of Drosophila melanogaster, I will identify the novel signaling mechanisms that replaced PDF signaling in M. abdita and test its role functionally in the maintenance of circadian rhythmicity in this species. Overall, these experiments will investigate a fascinating case of brain evolution leading to alternative solutions for a deeply conserved network communication mechanisms and create essential tools for the future study of the Megaselia species complex.

• DFG Programme: WBP Fellowship
• International Connection: Switzerland
• Host: Thomas O. Auer, Ph.D.