The goals of this research are to understand the biochemical and genetic factors involved in the regulation of tissue levels of glycosphingolipids particularly those involved in the assembly of lysosomal membranes and to understand genetic disorders that produce defects in lysosome structure. The human diseases, Chediak-Higashi syndrome and Hermansky Pudlak syndrome, are autosomal recessive disorders in which the underlying biochemical defects have not been identified. However, both disorders have lysosome and melanosome abnormalities and platelet storage pool deficiencies. They are, therefore, of interest both for their own sake and as an aid in understanding normal lysosome formation and function. A series of mouse pigmentation mutants have been identified with lesions and functional defects similar to the human disorders and offer a unique opportunity for elucidation of the molecular mechanisms involved. Each of the pigmentation mutants appears to have a unique primary genetic defect that affects the properties and assembly of lysosomal and other organellar membranes. We have shown that lysosomes are induced in the proximal tubule cells of the kidney of male and androgen treated female mice in both normal and mutant animals. Because the morphology of the testosterone induced lysosomes of each of the mutants that we have examined appears unique, it seems probable that each of the mutant lysosomes could have a different abnormal membrane component, either protein or lipid. Examination of the nature and metabolism of the membrane components in normal and mutant cells could lead to identification of secondary and perhaps primary defects and to identifi- cation of components that are required for normal lysosomal membrane assembly. We therefore will 1) characterize the kidney lysosomal membrane components from normal and mutant mice; 2) examine the metabolism of specific lysosomal membrane lipids in normal and mutant kidney cells in culture; 3) characterize testosterone responsive galactosyltransferase activities; 4) test for genetic homology of the mouse mutants with the related human disorders; 5) study the fusion of lysosomes of normal and mutant tissue culture cells in collaboration with Dr. Brian Storrie. The characterization of secondary and primary defects that affect lysosomal morphology and function should contribute to understanding the normal lysosome assembly processes as well as the molecular pathology of these inherited lysosomal diseases.
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