Immunohistochemical staining for Reelin in pig neocortex from five embryonic stages. A and B) Immunohistochemical staining of porcine cortex at E40. No staining was observed. C and D) Immunohistochemical staining of cortex at E60. Reelin expression is identified in CR cells of the marginal zone (MZ). B) Immunohistochemical staining at E60 at higher magnification. Black arrows indicate horizontal Reelin positive CR cells. Reelin immunoreactive interneurons in layer III-IV of the cortical plate is magnified (x10) in the box. E and F) Immunohistochemical staining at E80. Reelin expression is detectable with decreased intensity in the cortex. Bipolar fusiform CR type cells with dendrites oriented parallel with the pial surface were observed in the outer part of the MZ (open arrow) along with Reelin-immunoreactive interneurons and CR type cells displaying a variety of shapes and sizes. Reelin positive interneurons are seen in the CP but in decreased numbers. G and H) Immunoreactivity is observed in the cytoplasm of CR in the MZ at decreased numbers. The Reelin expression in the interneurons of the cortical plate is no longer detectable. I and J) Reelin positive cells are detectable in the outer part of MZ at E115. Scattered immunoreactivity is observed in the extracellular matrix throughout the CP. Cortical plate: CP; Marginal zone: MZ; pia mater: PIA; subplate: SP; VZ; subventricular zone: SVZ; 3rd ventricle: V; ventricular zone: VZ. Scale bar = 100 μm.