CAREER: Elucidating the Neuronal Basis of Sexual Dimorphism in the Drosophila Circadian System

The circadian system provides internal temporal order for an animal’s physiology and behavior. Circadian disruption has significant implications for health, and a growing body of evidence indicates the existence of sex differences in the circadian systems of many species. Drosophila is a powerful model system to study the neuronal basis of sexual dimorphism in timekeeping due to its well-characterized circadian clock neuron network and the highly conserved molecular circadian clock.

The main goal of this project is to understand how differences in the underlying architecture of the circadian system in the Drosophila brain underlie sex differences in sleep/wake cycles and robustness in timekeeping. Understanding the mechanistic basis of sexual dimorphism in the circadian system will inform our understanding of how males and females may be differentially affected by the challenges of complex modern environments.

The education plan of the project consists of a summer research program for undergraduate students to conduct research involving connectomics, neurogenetics, and behavior that will allow students to gain research experience in the interface of biology, bioinformatics, and engineering. In addition, community outreach efforts will be conducted in partnership with the Columbia Zuckerman Institute’s public outreach programs office.

They will involve participation in an event for families, Brain Clocks, in the context of the Saturday Science program, and a public event focused on conversations with New York City-based musicians in the context of the Breakout Science program, a series of interdisciplinary events that aims to create public engagement in science through the arts.

The circadian system provides internal temporal order for multiple aspects of physiology and behavior, allowing the anticipation of environmental changes. As in mammals, most of the work on Drosophila circadian rhythms has focused on males. The overarching hypothesis of this proposal is that sex differences in sleep/wake cycles are mediated by differences in the network properties of the brain’s timekeeping center.

In Aim 1, the research team will test the hypothesis that the sexually dimorphic phenotypes of the Pigment Dispensing Factor (PDF) / PDF receptor (PDFR) pathway mutations are due to differential effects of PDF signaling in the clock neuron network. The team will use time-course immunohistochemistry to compare expression rhythms of clock proteins and CRISPR-Cas9 to knockout PDFRs in subsets of clock neurons.

In addition, the team will determine if the PDFR-immunopositive neurons in females are less responsive to PDF-mediated Morning cell output using the ATP/P2X2 functional connectivity approach. In Aim 2, the team will test the hypothesis that the Morning oscillator has more influence over the male timekeeping neuronal network by changing the speed of the molecular clock in specific cell types and disrupting molecular oscillations in specific clock classes in males and females.

In Aim 3, the team will characterize sex differences in structural and functional connectivity patterns between the Dorsal Neurons 1 posterior (DN1p’s) and the Morning oscillator. The team will compare the strength of the DN1p connections to Morning and Evening cells and test the hypothesis that glutamatergic inhibition of the lateral clock neurons by DN1p’s is more pronounced in males than females analyzing physiological responses to bath-applied glutamate.

Collectively, the studies will advance our understanding of the mechanistic basis of differences in sleep/wake cycles between females and males.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.