X11α is a brain-specific protein.A, Total proteins extracted from mouse brain, kidney, and liver were resolved by 8% SDS-PAGE and transferred to nitrocellulose. Immunoblot with anti-X11α antibody detects X11α only in the brain. mLin-2/CASK is present in all tissues, as observed previously (Hata et al., 1996; Cohen et al., 1998). B, X11α-positive immunostaining in substantia nigra (SN). Scale bar, 300 μm. C, High magnification of the substantia nigra showing neuronal somata, with exclusion of the nucleus (open arrow) and positive dendrites (filled arrow). Scale bar, 50 μm.D, Same as B, but the anti-X11α antibody was preincubated with X11α peptide. E,In situ hybridization of rat brain with theX11α probe. The arrow shows the substantia nigra labeling. Scale bar, 0.2 cm.