[Abstract Title]. - Society for Neuroscience

they generally have an enlarged head portion that is connected to the dendritic shaft through a
narrow neck. This architecture enables spines to confine calcium ions and signalling events at
synapses. The structural plasticity of spines is believed to help regulate synaptic efficacy and is
dependent on actin filament remodelling. However, the signalling mechanisms that modulate
actin filament organization in spines remain to be fully described. Here, we present data
implicating the Slingshot 1L (SSH1L) phosphatase in controlling dendritic spine morphology.
SSH1L is known to dephosphorylate cofilin, an actin depolymerising/severing protein that
regulates actin filament dynamics and spine plasticity upon activity stimulation. We find that
SSH1L expression peaks during the first postnatal week of the mouse hippocampus, and
gradually declines toward adult stages. Interestingly, disruption of normal SSH1L signalling by
expression a phosphatase-inactive SSH1L in CA1 pyramidal neurons in organotypic
hippocampal slices cultures significantly alters dendritic spine morphology. The average length
of the head portion of spines is significantly increased while the width is decreased, resulting in a
larger percentage of elongated spines. Immunostaining for over-expressed wild type and
phosphatase-inactive SSH1L proteins in CA1 cells shows that the wild type form is concentrated
in the spine head region while the phosphatase-inactive form is enriched in the spine neck, with
weak expression at the tip of spine head. Our results suggest that SSH1L helps to control actin
cytoskeletal rearrangements that are important for regulating dendritic spine morphology.
Disclosures: L. Zhou, None; E. Jones, None; M. Haber, None; K. Murai, None.
Poster
239. Structural Plasticity at Synapses I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 239.14/E11
Topic: B.08.i. Structural plasticity
Support: CIHR
Canadian Stroke Network
MSFHR
Title: Imaging the emergence of new structural and functional circuits in the somatosensory
cortex of adult mice recovering from stroke in vivo
Authors: *C. E. BROWN 1 , T. H. MURPHY 2 ;
1 Dept Psychiatry, Univ. British Columbia, Vancouver, BC, Canada; 2 Psychiatry, Univ. of British
Columbia, Vancouver, BC, Canada