Two closely related proteins guide projections from nerve cells with exquisite accuracy, alternately attracting and repelling these axons as they navigate the nervous system to make remarkably precise connections, researchers from Johns Hopkins University have discovered.

Using embryonic flies, the team labeled particular classes of neurons and then observed them at high resolution using various microscopy strategies to compare their axon projections.

The team found that semaphorin/plexin interaction assures the establishment of precise connections between these central nervous system axons and sensory neurons that convey messages about the external environment.

They also completed experiments with genetically modified mice to demonstrate that semaphorins are necessary for neuronal projections from distinct classes of neurons to make their way to correct layers in the inner plexiform layer of the retina.

Ref: Zhuhao Wu, Lora B. Sweeney, Joseph C. Ayoob, Kayam Chak, Benjamin J. Andreone, Tomoko Ohyama, Rex Kerr, Liqun Luo, Marta Zlatic, Alex L. Kolodkin, A Combinatorial Semaphorin Code Instructs the Initial Steps of Sensory Circuit Assembly in the Drosophila CNS, Neuron, 2011; 70 (2): 281 DOI: 10.1016/j.neuron.2011.02.050

Ryota L. Matsuoka, Kim T. Nguyen-Ba-Charvet, Aijaz Parray, Tudor C. Badea, Alain Chédotal, Alex L. Kolodkin, Transmembrane semaphorin signalling controls laminar stratification in the mammalian retina, Nature, 2011; 470 (7333): 259 DOI: 10.1038/nature09675