Demonstration of the technique of colocalization of the GFP and the Y chromosome in a female brain at 2 months after PMCAO. Y chromosome hybridization was performed in sex-mismatched GFP BM-transplanted mice brains. (A) Presence of the Y chromosomes in red (Alexa-594); green fluorescence indicates the presence of the GFP, and blue fluorescence labels cell nuclei based on DAPI, a chromosomal stain. The section is one level of a Z-series demonstrating that the Y chromosome is localized in the same cells that are also GFP⁺ (side panels). (B) Cross-section of a capillary (*) of a Z-series depicting several luminally localized GFP cells that are also positive for the Y chromosome (red dots). The inset (C) shows another example, where the side panel of the confocal image illustrates that the Y chromosome and the GFP colocalize in a cell that borders the vascular lumen (*). Objective, 40×; numeric aperture, 0.6 (A); and objective, 20×; numeric aperture, 0.7 (B). Scale bar equals 16 μm.