1. DRG-Derived BDNF and Myelination
Benjamin K. Ng, Lian Chen, Wilhelm Mandemakers, Jos M. Cosgaya, and Jonah R. Chan

Although neurotrophic factors are usually considered to be target-derived secretory products that are then retrogradely transported to their site of action, this week Ng et al. provide more proof that BDNF can move in other directions. The authors examined the source of BDNF necessary for Schwann cell-mediated myelination of sensory nerves. BDNF expression increased soon after purified Schwann cells were cocultured with dorsal root ganglion (DRG) neurons. The expression was greatest prior to myelination. Using Campenot chambers, the authors report that BDNF was secreted from the compartment containing DRG axons as well as the cell body compartment, consistent with anterograde transport and secretion from the surface of the axons. Viralmediated gene transfer of myc-tagged BDNF into DRGs was later detected in Schwann cells, consistent with transfer of BDNF from DRG to Schwann cell. Overexpression of BDNF in DRGs also led to anterograde transport, secretion, and enhanced myelination.

2. Making Shaft Synapses
Jason Aoto, Pamela Ting, Bita Maghsoodi, Nanjie Xu, Mark Henkemeyer, and Lu Chen

Although excitatory synapses on dendritic spines seem to get most of the experimental attention, a subset of excitatory synapses end up on dendritic shafts. In some cells after all, such as many interneurons, there are no dendritic spines. Synapses on shafts are predicted to have distinct impacts on cell excitability based on differences in synaptic size and the electrotonic properties of dendrites. This week, Aoto et al. show that the formation of shaft synapses in cultured hippocampal pyramidal cells depends on so-called reverse ephrinB3 signaling. Reducing postsynaptic ephrinB3 by RNA interference decreased shaft synapses, whereas overexpression of ephrinB3 increased them. The effects of ephrin B3 knockdo
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Contact: Sara Harris
sharris@sfn.org
202-962-4000
Society for Neuroscience
10-Jul-2007