Fig. 3.

Observations of the patterns of X-gal-labeled dentate granule cells. A, Example of a chimera (chimera 12) with many X-gal-labeled cells in the outer shell of the dentate granule cell layer and very few X-gal-labeled cells in the inner core.B, Example of a chimera with many X-gal-labeled cells in the inner core of the dentate granule cell layer and no X-gal-labeled cells in the outer shell (chimera 6). The diffuse bluelabel in the molecular layer is associated with the dendrites of labeled granule cells. This is a characteristic of the LacZ reaction product in the H253 transgenic line used for blastocyst-injection chimeras. C, Example of a mirrored-image pattern of like-genotype granule cells in the inner core of each blade of the dentate gyrus. In this chimera (chimera 9), X-gal-labeled granule cells in the apex and blade tips of the granule cell layer form mirrored-images of each other. D, Three-dimensional reconstruction of the left dentate gyrus of a low-percentage chimera (chimera 6) demonstrating the spatial restrictions of like-genotype cohorts of granule cells. Thetable on the left shows the number of X-gal-labeled cells and the estimated total number of granule cells in each analyzed section. The overall percentage of X-gal-labeled cells of the total granule cell population is shown at thebottom. The percentage of X-gal labeling of the total granule cell population for similar segments of the dentate gyrus of two other low-percentage chimeras (chimeras 10 and 11) is shown in thetable on the right. Scale bar (A–C): 110 μm.