Histology at age 11–12 months (A) hASA-C69S expression in the CNS of transgenic ASA−/− mice. Immunostaining of brain stem (A1) and cerebellum (A2) detects high hASA-C69S levels in neuronal perikarya of brain stem nuclei and the Purkinje cell layer (arrow). (B) Co-immunostaining of hASA-C69S (red) and F4/80 (green) reveals low transgene expression levels in liver (B1). Higher magnification (B2) detects expression in some F4/80-negative (open arrows) and -positive cells (closed arrows) with small nuclei, but not in hepatocytes (one nucleus is indicated by an arrowhead). (C) Cervical spinal cord of a conventional (C1–C3) and a transgenic ASA−/− mouse (C4–C6). Sections (100 µm) were incubated with alcian blue to visualize sulfatide storage. C1, C4 — overviews to outline the regions shown at higher magnification. gm — gray matter, wm — white matter, dh — dorsal horn, dt — dorsal tract, vh — ventral horn. (D) Alcian blue-incubated sections (100 µm) through kidney of a conventional (D1, D2) and a transgenic ASA−/− mouse (D3, D4). D1, D3 — overview; regions shown at higher magnification are boxed. Storage material is seen in the thick ascending limbs of Henle’s loop (TAL) of the inner (iS-oM) and outer stripe of the outer medulla (oS-oM), and to a lesser extent in the TALs of the medullary rays of the cortex (Co). D2, D4 — cortex. (E) Electron micrographs of hepatocytes. E1 — wildtype control mouse; E2, E3 — transgenic mouse expressing hASA-C69S on the wildtype background (serum level 0.91 µg/mL). Most lysosomes of the transgenic mouse show a normal morphology (asterices). However, some contain glycogen particles (open arrows in E3). Autophagic vacuoles do not contain glycogen (closed arrow). gl — cytosolic glycogen, bc — bile canaliculus, arrowheads — cell boundary.