Fig. 1.

p73 and Reelin are coexpressed by CR cells in human neocortex. In this and the following figures, the p73 immunoreaction product is black and localized to the nucleus, whereas Reln staining is light brown oryellow and localized to the cytoplasm. The variable intensities of p73 immunostaining depend on tissue and pretreatment rather than on the age. A, 10 GW. In the initial stages of the cortical plate, most CR cells in the MZ coexpress both proteins, although in lateral areas (B) a small proportion of CR are p73-immunonegative, Reln-IR (arrow); they are not seen in older brains.C, 17 GW. CR cells increase in number and display a variety of shapes and orientations. At this stage, virtually all Reln-IR cells express p73. D, 20 GW. p73/Reln-IR CR cells acquire a vertical orientation and elongate soma. Cresyl violet stains the granule cells of the SGL, which are Reln- and p73-negative.E, 22 GW. CR cells descend to deeper levels of the MZ and extend long ascending processes. F, A deep CR cell at 27 GW displays cytoplasmic vacuoles (arrows) and loss of processes, indicating degenerative decline. G,(Reln); H, (p73/Reln): 28 GW. A perinatal CR cell variety coexpressing p73 and Reln develops in a subpial position. In parallel, a population of small Reln-IR cells appears scattered throughout the MZ; they are p73-negative and weakly immunopositive for Reln (G, H, arrows). I, 43 years, Reln. Interneurons of adult layer I express Reln, but are p73-negative.J–L, Examples of double p73/Reln-positive neurons that are rare in postnatal life. J, 3 months; K, L, 43 years. Scale bars: A–D, 10 μm;E, 25 μm; F, 15 μm;G–J, 20 μm; K, L, 15 μm.