PT  - JOURNAL ARTICLE
AU  - Georgia F. Woods
AU  - Won Chan Oh
AU  - Lauren C. Boudewyn
AU  - Sarah K. Mikula
AU  - Karen Zito
TI  - Loss of PSD-95 Enrichment Is Not a Prerequisite for Spine Retraction
AID  - 10.1523/JNEUROSCI.6662-10.2011
DP  - 2011 Aug 24
TA  - The Journal of Neuroscience
PG  - 12129--12138
VI  - 31
IP  - 34
4099  - http://www.jneurosci.org/content/31/34/12129.short
4100  - http://www.jneurosci.org/content/31/34/12129.full
SO  - J. Neurosci.2011 Aug 24; 31
AB  - Changes in neuronal structure are thought to underlie long-term behavioral modifications associated with learning and memory. In particular, considerable evidence implicates the destabilization and retraction of dendritic spines along with the loss of spine synapses as an important cellular mechanism for refining brain circuits, yet the molecular mechanisms regulating spine elimination remain ill- defined. The postsynaptic density protein, PSD-95, is highly enriched in dendritic spines and has been associated with spine stability. Because spines with low levels of PSD-95 are more dynamic, and the recruitment of PSD-95 to nascent spines has been associated with spine stabilization, we hypothesized that loss of PSD-95 enrichment would be a prerequisite for spine retraction. To test this hypothesis, we used dual-color time-lapse two-photon microscopy to monitor rat hippocampal pyramidal neurons cotransfected with PSD-95-GFP and DsRed-Express, and we analyzed the relationship between PSD-95-GFP enrichment and spine morphological changes. Consistent with our hypothesis, we found that the majority of spines that retracted were relatively unenriched for PSD-95-GFP. However, in the subset of PSD-95-GFP-enriched spines that retracted, spine shrinkage and loss of PSD-95-GFP were tightly coupled, suggesting that loss of PSD-95-GFP enrichment did not precede spine retraction. Moreover, we found that, in some instances, spine retraction resulted in a significant enrichment of PSD-95-GFP on the dendritic shaft. Our data support a model of spine retraction in which loss of PSD-95 enrichment is not required prior to the destabilization of spines.