Neuronal contact predicts connectivity in the C. elegans brain

Axons must project to particular brain regions, contact adjacent neurons, and choose appropriate synaptic targets to form a nervous system. Multiple mechanisms have been proposed to explain synaptic partnership choice. In a lock-and-keymechanism, first proposed by Sperry's chemoaffinity model,1 a neuron selec-tively chooses a synaptic partner among several different, adjacent target cells, based on a specific molec-ular recognition code.2 Alternatively, Peters' rule posits that neurons indiscriminately form connections with other neuron types in their proximity; hence, neighborhood choice, determined by initial neuronal process outgrowth and position, is the main predictor of connectivity.3,4 However, whether Peters' rule plays an important role in synaptic wiring remains unresolved.5 To assess the nanoscale relationship between neuronal adjacency and connectivity, we evaluate the expansive set of C. elegans connectomes. We find that synaptic specificity can be accurately modeled as a process mediated by a neurite adjacency threshold and brain strata, offering strong support for Peters' rule as an organizational principle of C. elegans brain wiring.

Automated summary

The selection of synaptic connections can be explained by adjacency and cellular arrangement, supporting Peters' rule. By evaluating the connectome of C. elegans, it is found that synaptic specificity can be accurately modeled by neurite adjacency and brain strata, providing strong support for Peters' rule as an organizational principle of C. elegans brain wiring.