Figure 1.

Distribution of SAP102 and PSD-95 in spines. A, Double staining of endogenous SAP102 (red) and PSD-95 (green) in hippocampal neurons (21 DIV). Both SAP102 and PSD-95 are enriched in spines relative to dendrites and are highly colocalized in spines but not in dendrites (more pictures in supplemental Fig. 2, available at www.jneurosci.org as supplemental material). Scale bar, 2 μm. B, High-magnification image of a mushroom spine that was double stained for endogenous SAP102 (red) and PSD-95 (green). Scale bar, 200 nm. C, Fluorescence intensity of SAP102 (red line) and PSD-95 (green line) along the yellow marker in panel B. The x-axis shows the distance from the left end of the yellow marker, and the y-axis is the fluorescence intensity. D, Immunogold labeling of SAP102 and PSD-95 in spines from CA1 stratum radiatum of the 37-d-old rat hippocampus. SAP102 is localized at the PSD (arrowhead) as well as in the cytoplasm (arrow), while PSD-95 is concentrated at the PSD (arrowhead). a, b, Single immunogold labeling of PSD-95 (a) or SAP102 (b) using 10 nm gold (2 animals for each). c, d, Sections that were double labeled for PSD-95 (15 nm gold) and SAP102 (5 nm gold) show distributions indistinguishable from those that were single labeled (2 animals). P, Presynaptic terminal. Scale bar, 100 nm. E, Distribution of gold particles in spines from CA1 stratum radiatum of P37 rat hippocampus. There is an overlap in the localization of PSD-95 and SAP102. The median values (dash lines) are 13.5 nm from the postsynaptic membrane for PSD-95 and 24.2 nm from the postsynaptic membrane for SAP102. SAP102 is more generally distributed in the cytoplasm between 50 and 250 nm from the postsynaptic membrane. Data are from both single and double labeling of SAP102 or PSD-95 (n = 294 for PSD-95, including n = 192 from single labeling and n = 102 from double labeling; n = 283 for SAP102; including n = 144 from single labeling and n = 139 from double labeling). PSM, Postsynaptic membrane.