A fundamental design principle of nervous systems is the grouping of neuronal contacts into layers within nerve bundles. The layered arrangement of neurites requires nanoscale precision in their placement within bundles, and this precision, which can not be exclusively explained by simple tip-directed outgrowth dynamics, underpins synaptic specificity and circuit architecture. Here we implement novel imaging methods and deep learning approaches to document the specific placement of single neurites during the assembly of the C. elegans nerve ring. We uncover a zippering mechanism that controls precise placement of neurites onto specific layer subdomains. Nanoscale precision in neurite placement is orchestrated via temporally-regulated expression of specific Ig adhesion molecules, such as SYG-1. Ig adhesion molecules act as instructive signals, defining sublaminar regions and guiding neurite zippering onto target neurons. Our study reveals novel developmental mechanisms that coordinate neurite placement and synaptic specificity within layered brain structures.
bioRxiv Subject Collection: Neuroscience