Yip ZC et al. (2018) Elife "Ordered arrangement of dendrites within a C. elegans sensory nerve bundle."

[

Elife,

2018]

Biological systems are organized into well-ordered structures and can evolve new patterns when perturbed. To identify principles underlying biological order, we turned to <i>C. elegans</i> for its simple anatomy and powerful genetics. We developed a method to quantify the arrangement of three dendrites in the main sensory nerve bundle, and found that they exhibit a stereotyped arrangement throughout larval growth. Dendrite order does not require prominent features including sensory cilia and glial junctions. In contrast, loss of the cell adhesion molecule (CAM) CDH-4/Fat-like cadherin causes dendrites to be ordered randomly, despite remaining bundled. Loss of the CAMs PTP-3/LAR or SAX-7/L1CAM causes dendrites to adopt an altered order, which becomes increasingly random as animals grow. Misexpression of SAX-7 leads to subtle but reproducible changes in dendrite order. Our results suggest that combinations of CAMs allow dendrites to self-organize into a stereotyped arrangement and can produce altered patterns when perturbed.

Yip ZC et al. (2016) Cell Rep "Duplication of a Single Neuron in C.elegans Reveals a Pathway for Dendrite Tiling by Mutual Repulsion."

Heiman MG, Yip ZC

[

Cell Rep,

2016]

Simple cell-cell interactions can give rise to complex cellular patterns. For example, neurons of the same type can interact to create a complex patchwork ofnon-overlapping dendrite arbors, a pattern known as dendrite tiling. Dendrite tiling often involves mutual repulsion between neighboring neurons. While dendrite tiling is found across nervous systems, the nematode Caenorhabditis elegans has a relatively simple nervous system with few opportunities for tiling. Here, we show that genetic duplication of a single neuron, PVD, is sufficient to create dendrite tiling among the resulting ectopic neurons. We use laser ablation to show that this tiling is mediated by mutual repulsion between neighbors. Furthermore, we find that tiling requires a repulsion signal (UNC-6/Netrin and its receptors UNC-40/DCC and UNC-5) that normally patterns the PVD dendrite arbor. These results demonstrate that an apparently complex cellular pattern can emerge ina simple nervous system merely by increasing neuron number.