Prlhr localizes to cilia in the hypothalamic third ventricle.

A–D) Prlhr was localized to the ventricular cilium in the adult mouse brain. Frozen sections containing the third ventricle of the adult mouse brain were immunostained with an anti-Prlhr antibody (green). The Prlhr signal was observed in cilia protruding from cells on the surface of the third ventricle (arrowheads in A, B, D). Preabsorption of the anti-Prlhr antibody with a synthetic Prlhr-peptide antigen abolished the Prlhr staining in the cilia (C). Cilia were coimmunostained with an anti-Arl13b antibody (D, red). Cilia with the Prlhr signal (arrowheads) were not clustered together, unlike the multiple cilia of ependymal cells that lacked the Prlhr signal (arrows). E–H) Ventricular Prlhr-positive cilia (red) were double stained with GFAP (green) which stains a subtype of tanycytes. A partial population of the GFAP-positive tanycytes (green) possesses Prlhr-positive cilia (arrowheads). Nuclei were stained with DAPI (blue). V: third ventricles. Scale bars, 20 μm (the left panel in A; B, C, F, G), 10 μm (the right panel in A; H), 5 μm (D), and 40 μm (E).