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. 2006 Feb 1;26(5):1355–1365. doi: 10.1523/JNEUROSCI.3164-05.2006

Figure 5.

Figure 5.

SynGAP expression in the developing cortex and thalamus. Histochemistry for β-galactosidase to reveal the expression profile of Syngap in the S1 (a, b) and thalamus (c, d) at P4 (a, c) and P8 (b, d). For a complete developmental series, see supplemental Figure 2 (available at www.jneurosci.org as supplemental material). In cortex, β-gal is first expressed at P0 in layer 4 of the developing cortical plate. By P4, staining can be seen throughout the supragranular layers as well as layer 4 and the upper region of layer 5. It is also present in a thin strip of cells located at the bottom of the cortical plate (a). By P8, staining can be seen throughout the cortical plate, and the barrels are clearly distinguished in layer 4 (c). By adulthood, staining has been dramatically reduced and can only be seen at the layer 4/5 border and in layer 1. A similar developmental profile can be seen in the VB and throughout the dorsal thalamus with strong staining visible at P4 (c) and P8 (d) and reduced expression in adults. Immunohistochemical localization of SynGAP protein at P7 (e–g) is in good agreement with β-gal localization. Low-power images show high levels of SynGAP in the cortex (C), hippocampus (H), and amygdaloid complex (A) with lower levels in the VB of the thalamus. In S1 (f), SynGAP levels are highest in layer 4, and the supragranular layers and barrels can be clearly seen. Expression is just starting to appear in the infragranular layers, although a dense band of label can be seen at the layer 4/5 border. The immunohistochemical localization therefore is in good agreement with the large increase in X-Gal staining between P4 and P7. In thalamus, SynGAP is expressed throughout the VB. Electron microscopy analysis of SynGAP expression in layer 4 at P14 reveals a postsynaptic localization for SynGAP (h–j). DAB reaction product can be clearly seen as dark labeling in the PSD (asterisks) opposing presynaptic terminals containing synaptic vesicles. In h, three PSDs in tandem on the shaft of a dendrite are clearly visible. Higher magnification of the middle synapse in h shows clear amalgamation of presynaptic vesicles abutting the SynGAP-positive PSD. Clear presynaptic vesicles are also seen in j. Reaction product was never seen in axons or axon terminals. Scale bar (in j): a, b, 200 μm; c, d, 400 μm; e, 775 μm; f, 150 μm; g, 275 μm; h, 250 nm; i, 175 nm; j, 100 nm.