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Figure 4: DCX-labeled basal dendrites grow along an ectopic glial scaffold. Confocal micrographs depicting DCX+ (a, d, g), GFAP+ (b, e, h), and merged, double-labeling for DCX (green) and GFAP (red) at 30 days after FPI. Note that (a)–(c) are taken from the infrapyramidal blade, whereas (d)–(i) are taken from the suprapyramidal blade. As can be seen in (a), (d), (g), DCX+ basal dendrites (arrows) are prominent features after FPI, and many of these basal dendrites extend deep into the hilus. Also note, in (b), (e), and (h), the hypertrophied appearance of GFAP+ cells at the base of the granule cell layer (arrowheads). Also note that the predominant orientation of the astrocytes from FPI mice at the border of the granule cell layer is oriented either parallel with the granule cell layer or toward the hilus. Such an orientation is consistent with an ectopic glial scaffold. The lack of radial glial processes extending through the granule cell layer is also notable in (b) and (h). In the merged images (c, f, i) the close relationship between the DCX+ basal dendrites and the GFAP+ processes can be appreciated (arrows). In (i), the apposition of the basal dendrite with the GFAP+ is so close that the two processes almost appear as if they are intertwined (arrowheads). Future studies using electron microscopy will determine if these cells/processes are aberrantly targeted for synaptogenesis in the hilus. Scale bars in (a)–(c) & (g)–(i) = 10 µm and in (d)–(f) = 20 µm. In (f) and (i), the appositions of the basal dendrites to the GFAP+ processes are so close that the two almost appear as if they are intertwined.