Abstract
The brain is a versatile system and consists of an intricate network of neurons that communicate with each other through special cell contact sites- synapses. Each neuron sends its axon to travel long distance, to meet appropriate targets and to make synapses. The axonal outgrowth and synaptogenesis are regulated by various proteins which exist on cells surface or in the extracellular environments. For investigating the effects of various exogenous proteins on axonal outgrowth and pre-synaptic specification, a chip-based system has been developed. The system comprises of multiple micropatterned areas mounted on the surface of a glass chip. Neurons are cultured on one area on the chip with their axons being guided to grow in another area on the same surface. The amount of axons and of the clusters of releasing-competent synaptic vesicles (RSV), a marker of pre-synaptic specification, in this latter area can be quantified. In this system, various proteins can be coated to a specific area where axons grow. By quantifying the different amounts of axons and pre-synaptic specification in this specific area, the effects of different proteins can be compared and investigated. The effects of neuroligin 1, laminin, and collagen on axonal outgrowth as well as pre-synaptic specification have been studied here by using this system. A protein can also be coated at varied areas, and thereby different regions of neurons are exposed to this single protein. The amounts of axons and pre-synaptic specification under such conditions can also be quantified. Thus, the effective signal range of a specific protein that could travel within a neuron can be investigated. By using this method, neurolign1 has been studied and demonstrated to mediate pre-synaptic specification within short ranges.