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Bentley et al. 2016

The Multilayer Connectome of Caenorhabditis elegans

Barry Bentley, Robyn Branicky, Christopher L. Barnes, Yee Lian Chew, Eviatar Yemini, Edward T. Bullmore, Petra E. Vértes , William R. Schafer
PLoS Comput Biol 12(12): e1005283
Published: December 16, 2016

Abstract:

  • Extrasynaptic modulation (monoamines and peptides) influence neural circuits
  • This paper presents a draft monoamine connectome and a partial neuropeptide connectome, based on new and published expression data for biosynthetic genes and receptors

Introduction

  • A full understanding of neural connectivity requires a detailed mapping of these extrasynaptic pathways
  • Monoaminergic systems play diverse roles in regulating behaviour and so extrasynaptic monoamine interactions must also be mapped, not just the network of wired chemical synapses and gap junctions
  • Neuropeptides are widely used as neuromodulators in the C.elegans nervous system, with over 250 known or predicted neuropeptides from at least 122 precursor genes and over 100 putative peptide receptors

Materials & Methods

  • Full hermaphrodite C.elegans connectome, containing all 302 neurons
  • Network was composed from somatic connectome of White et al, updates and released by Chklovskii lab
  • Pharyngeal network of Albertson and Thomson made available by the Cybernetic C.elegans Program CCeP
  • Functional classifications referred (i.e. sensory neuron, interneuron, motor neuron) are based on the classification scheme used in WormAtlas

Monoamine network construction

  • A literature search was performed to identify genes known to be receptors, transporters or synthetic enzymes of monoamines
  • A further search was performed to collect cell-level expression data for the monoamine associated genes identified in the previous step
  • Search was assisted with WormBase databases and WormWeb
  • Neurons expressing multiple receptors for a single monoamine receive a single edge from each sending neuron
  • Reciprocal connections between nodes are considered as 2 separate unidirectional connections

Neuropeptide network construction

  • Constructed from published expression data for peptides and receptors using similar methods for the monoamines
  • Only those systems were included for which sufficient expression and ligand-receptor interaction data in the literature (biologically plausible EC50 values)
  • 15 neuropeptides and 12 receptors were matched and included.