Figure 1.

Developmentally generated columns of cells in cortex contain both neurons and astrocytes. A, B, Adult TFC.09 × Z/EG mice exhibit radially arrayed columns of cells in cortex apparent both along the sagittal (A) and coronal (B) planes. These columns of cells display the characteristic morphologies of developmental columns generated in previous cortical clonal labeling experiments using other methods. C, These columns of GFP labeled cells (white) contained both neurons and astrocytes, which have been pseudocolored blue for the purposes of visualization. C, D, F, G, We measured whether GFP+ astrocytes were in (blue lines), near (within 50 μm as indicated by the red lines), or outside of GFP+ columns. Columns were defined as discreet, elongated structures in the cortex that contained GFP+ cells with unambiguous pyramidal neuron morphologies spanning from the ventricular to the pial surface. F, G, We measured the distance between astrocytes (blue) and their nearest neighboring neuron (green) to assess their spatial relationship. The average distance between an astrocyte and its nearest neighbor was 33 ± 28 μm. H, I, We assessed neuronal density as a function of distance, measuring the density of neurons within 100 μm of an astrocyte, 200 μm, 300 μm, etc. Astrocytes were found in regions of high neuronal density, as would be expected of astrocytes located within neuronal columns. J, Astrocytes were found associated with neuronal columns even when the columns were curved, as they are commonly in the occipital cortex, suggesting their association is not merely accidental. K, In piriform cortex, with its three-layered structure that is distinct from neocortex, neither layer 2 interneurons nor astrocytes exhibited columnar organization, demonstrating that the columnar structures we found in neocortex are unlikely to be artifactual. Scale bars: A, B, M, N, 500 μm; D, J, K, 100 μm; C, F, H, 50 μm.