A chip-based method for studying the effects of exogenous proteins on neuronal axons

Axons are long, slender processes of neurons that have various functions at different stages of development. Here, we report the use of a chip device to study the effects of various exogenous proteins on the growth and presynaptic differentiation of axons in a high-throughput manner. The device consists of a glass chip whose surface contains a protein-coated micropattern. When neurons are maintained on the chip, a specific region of the chip surface will be occupied exclusively by axons. The axons and clusters of release-competent synaptic vesicles, a presynapse-like specialization in the axon, can be quantified as the proportions of this specific region's area occupied respectively by these subcellular structures. By using chips with this specific region coated with different proteins, these proteins' effects on the growth and presynaptic differentiation of the axon were investigated by comparing the amounts of axons and clusters of release-competent synaptic vesicles in this region of the chip. We also demonstrate another application of this chip device by investigating the effective range of the signal produced by the interaction between neurons and neuroligin 1 in neurons. These results indicate the diverse applications of the chip device in exploring various issues pertaining to axonal functions.