Automated Platform for High-Content Cardiac Drug Screening in Drosophila

McFaul, Christopher 1, 2, 5 ;  Yip, Christopher 2, 3 ;  Fernandez-Gonzalez, Rodrigo 2, 4, 5

1. MD/PhD Program, University of Toronto; 2. Institute of Biomaterials and Biomedical Engineering, University of Toronto; 3. Departments of Biochemistry, Chemical Engineering and Applied Chemistry, University of Toronto; 4. Department of Cell and Systems Biology, University of Toronto; 5. Ted Rogers Centre for Heart Research, Translational Biology and Engineering Program, University of Toronto

Primitive heart tube formation in the Drosophila embryo requires tight spatio-temporal regulation of cardiac transcription factors that regulate cell fate and positioning. While the genetic pathways that induce cardiac progenitors in the fly have been well studied, the mechanisms that regulate cell-cell interactions and migration are not well understood. In Drosophila, the heart is formed from 52 bi-lateral pairs of cardiac precursors that migrate dorsally and medially to join their contralateral counterparts. The cells must then undergo distinct morphological changes to control sites of adhesion and repulsion to their partner in order to form a proper lumen. We hope to better understand the coordinated cell-cell interactions and cytoskeletal rearrangements that lead to cardiac tube formation. Leveraging the simplicity and pharmacological tractability of the fruit fly, Drosophila melanogaster, and the ability to perform live imaging in its embryos, we will conduct a pharmacological screen for compounds that disrupt cardiac tube formation. We are developing a platform for high-content,  in vivo drug screening using a spinning disk confocal microscope coupled to an automated embryo injection system. The platform will automatically identify, inject and image embryos co-expressing fluorescent forms of the junctional protein E-cadherin and the cytoskeletal protein F-actin. These markers will allow us to identify and track cardiac and overlying epidermal cells and visualize the molecular rearrangements associated with heart tube formation, which we will quantify by automated image analysis. As a follow-up to the pharmacological effects on heart tube formation, we will also perform in toto light-sheet microscopy of the embryos to screen for off-target drug effects. Together, our novel tools will allow us to identify pathways critical for cardiac precursor migration, polarization and cell-cell adhesion.