News tips from the Journal of Ne...( 1. Postsynaptic Scaffolds on the Move ...)

Generally, it's not a good idea to shake or move a ladder sideways with someone on it. However, that seems to be exactly what synaptic scaffolding proteins do. In this week's Journal, Hanus et al. monitored the GABA/glycine receptor scaffold gephyrin by tagging it with the yellow fluorescent protein derivative Venus. Cultured neurons were transfected on day 8 and then imaged 12 d later. In rat spinal cord neurons, Venus:gephyrin chimeras clustered on postsynaptic dendrites, but time-lapse imaging revealed submicron lateral movements. Gephyrin cluster movements were much faster than global dendritic movements. The authors suggest that fast (<5 seconds) and slower (>10 seconds) components corresponded to shifts within clusters and lateral movement of clusters. Both actin dynamics and microtubules affected the movements, perhaps not surprising given the location of these inhibitory synapses on dendritic shafts. Enhancement of neural activity diminished the scaffold movements.

2. Migrating with MDGA1
Akihide Takeuchi and Dennis D. M. O'Leary

This week, Takeuchi and O'Leary outline a developmental role for MAM domain glycosylphosphatidylinositol (GPI) anchor1 (MDGA1), a recently cloned Ig cell adhesion molecule. This glycoprotein is anchored to the extracellular membrane by a GPI linkage and is similar in structure to Ig-containing cell adhesion molecules such as L1. Because layer 2/3 mouse neurons expressed MDGA1 during development, but not adulthood, the authors hypothesized that MDGA1 was important for cell migration. They suppressed MDGA1 expression in mouse brains with RNA interference delivered by electroporation in utero. Transfections were timed to embryonic day 15.5 so that most transfected cells were destined to become layer 2/3 neurons. Without MDGA1, layer 2/3 neurons were trapped in the intermedia
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Contact: Sara Harris
sharris@sfn.org
202-962-4000
Society for Neuroscience
25-Apr-2006