Fig. 1

Schematic of experimental designs used to establish neuronal circuits using microfluidic devices. Neurons expressing the tetraspanin CD9 together with either a red or green fluorescent tag were used to track exosomal, endosomal and plasma membranes. a Model 1 of two differently colored neurons (A-red and B-green) seeded separately into the two chambers Ch1 and Ch2. Red axons extend from Ch1 to Ch2, but green axons can also project from Ch2 to Ch1. The potential combination of colors by transmission of exosomes is shown in yellow. b Model 2 of three interconnected neurons (A-green, B-red, C-no color) seeded into chambers Ch1 and Ch2. The exosomes from A (green) are internalized by B (red) and can potentially be anterogradely transported to C (no color). Combination of colors is shown in yellow. The gradient of the triangle depicts a hydrostatic pressure gradient that prevents diffusion from Ch1 to Ch2. Note that sizes of neurons and culture chambers are not shown at scale