Light and electron microscopic analysis of the central and peripheral nervous systems of acid sphingomyelinase-deficient mice resulting from gene targeting.

The acid sphingomyelinase (aSmase)-deficient mouse line recently generated by gene targeting (Otterbach and Stoffel, 1995) develops a lethal storage disease which is phenotypically comparable to the neurovisceral form of the human sphingomyelinosis, Niemann-Pick disease type A (NPA). This report describes the progressive accumulation of uncatabolized lipid substrates at the cellular and ultrastructural level in different regions of the nervous system of homozygous aSmase-/- mice, including cerebrum, cerebellum, spinal cord, optic nerve and peripheral nerves. We saw a cytoplasmic accumulation of pleomorphic lysosomal structures in cells of all regions under study, most extensively in macrophages, vascular endothelial cells, and also in neuronal perikarya. The complete and early degeneration of Purkinje cells was particularly striking. Moreover, we found a storage material in the cytoplasm of Schwann cells and to a minor extent in oligodendrocytes. In most advanced stages of the disorder, we detected an axonal dystrophy in both the central nervous system (CNS) and peripheral nervous system (PNS), without signs of dysmyelination or demyelination. The morphological changes of the central and peripheral nervous systems in the homozygous aSmase-/- mouse line closely resemble those in human NPA.