Toegel et al. (2017) developed a customizable binary expression system based on bacterial transcription activator-like effector (TALE) fusion proteins. Since TALEs can be programmed to bind any DNA sequence, this platform could enable the generation of virtually unlimited driver–responder pairs suitable for independent parallel transgene expression in vivo. By analogy to the GAL4 upstream activating sequence (UAS), they termed the programmable TALE responder binding sites variable activating sequences (VAS). TALE drivers and VAS responders can be combined in vivo to enable simultaneous expression of multiple transgenes in interacting tissues, without apparent crosstalk between individual pairs. Furthermore, the TALE–VAS system can be used in conjunction with other binary expression platforms.

TALE and VAS socks are available on our TALE/VAS page.