PXGS: a Poly-Transgene Expression System based on Mutually Exclusive Splicing of Dscam

Biologists often need to investigate multiple genes simultaneously in an organism. However, it is currently not possible to express more than a few transgenes in an animal under conditional control. Here, we developed a technique based on the mutually exclusive splicing of the Down Syndrome Cell Adhesion Molecule1 (Dscam1) gene in Drosophila melanogaster to achieve simultaneous transgene expression of 12 genes at a time. We show that the hypervariable Dscam1 exon 4 region maintains its alternative splicing when placed in a UAS expression vector. Each of the twelve exon 4 alternates can be replaced with an exogenous gene of at least 10 kilobases and will express properly in vivo all under conditional genetic control. We demonstrate the expression of four different fluorophores placed in different exon 4 alternate positions in neural and non-neural cells in vivo. We validated the technique by rewiring Drosophila sensory neuron axons in vivo by simultaneously expressing several cell surface receptors within the neuron. This technology will also enable Drosophila melanogaster as a model system for synthetic biology research.