| The gangliosidoses are a group of fatal, inherited metabolic diseases which occur due to the lack of a specific lysosomal enzyme responsible for the degradation of various cellular waste products. The enzyme deficiencies result in storage of undegraded substrate in visceral organs and the nervous system. In their most severe form, the disorders present in early childhood and result in death by three to four years of age. Animal models of the gangliosidoses exist in mouse and some non-rodent species. This report details research aimed at characterization and therapy of feline models of GM1 and G M2 gangliosidosis.;Although bone marrow transplantation (BMT) ameliorates some storage diseases, many lysosomal disorders are refractory to such treatment for reasons not fully understood. After transplantation, bone marrow-derived cells migrate to the central nervous system where they effectively supply some, but not all, lysosomal enzymes to diseased neurons. In an attempt to elucidate the mechanism behind the variable success of bone marrow transplantation for lysosomal disorders, the authors studied feline enzymes whose deficiencies have been treated effectively and ineffectively with BMT. Experiments were performed to evaluate the stability and secretion of the lysosomal enzymes alpha-mannosidase and beta-galactosidase. The data suggests that enzyme transfer from donor to recipient cells is not dependent on enzyme stability or secretion but on the suitability of secreted enzyme for endocytosis. This information will support future studies designed to optimize secreted lysosomal enzymes for endocytosis by diseased cells.;Because transplantation of normal bone marrow into diseased individuals does not alter clinical progression of the gangliosidoses, any marrow-based therapy of these disorders requires alteration of native enzyme to enhance therapeutic efficacy. Therefore, a method of delivering altered enzyme to donor bone marrow was developed. A replication-defective retroviral vector was constructed and utilized to transfer lysosomal enzyme to diseased feline cells, thereby establishing the validity of this delivery system for the feline gangliosidosis models.;GM2 gangliosidosis results from lack of beta-N-acetylhexosaminidase, which cleaves terminal N-acetylgalactosamine residues from a variety of substrates, including GM2 ganglioside. Molecular characterization of the disease mutation responsible for a feline model of GM2 gangliosidosis was undertaken in this study and found to be a small inversion at the extreme 3' end of the coding sequence. In addition to providing valuable information for precise genotypic characterization of GM2 gangliosidosis disease carriers, the inversion provides a natural model for the study of mutations near the end of the coding sequence of hexosaminidase. |
