Rapid formation and remodeling of postsynaptic densities in developing dendrites

The dynamics of postsynaptic density (PSD) formation and remodeling were in vestigated in live developing hippocampal tissue slices. Time lapse imaging of transfected neurons expressing GFP-tagged PSD95, a prominent PSD protei n, revealed that up to 40% of PSDs in developing dendrites are structurally dynamic; they rapidly (<15 min) appear or disappear, but also grow, shrink and move within shafts and spines. New spines containing Ms were formed by conversion of dynamic filopodia-like spine precursors in which PSDs appear ed de novo, or by direct extension of spines or spine precursors carrying p reformed PSDs from the shaft. Ms are therefore highly dynamic structures th at can undergo rapid structural alteration within dendrite shafts, spines a nd spine precursors, permitting rapid formation and remodeling of synaptic connections in developing CNS tissues.