Sanfilippo B syndrome is a recessively inherited disorder caused by the deficiency of a lysosomal enzyme, alpha-N-acetylglucosaminidase. It is primarily a neurological disease with relatively mild somatic disorders. I propose to generate a mouse "knockout" model for Sanfilippo B. The specific goal includes the cloning and characterization of a mouse gene (Naglu) encoding alpha-N-acetylglucosaminidase, the construction of a vector for disruption of the Naglu gene, the generation of the mutant mouse, and the characterization of its phenotype. The Naglu gene will be isolated from a mouse genomic library, and the entire gene will be placed ina vector which contains suitable selectable markers. The resulting construct will be transfected into cultured mouse embryonic stem (ES) cells and selected for homologous recombination. Selected ES cells will be used for injection into blastocytes to generate chimeric and eventually homozygous mutant mice. The phenotype of the "knockout" mouse will be characterized for alpha-N-acetylglucosaminidase activity and accumulated heparan sulfate, the substrate for the enzyme, in various organs. The brain of the mutants will be analyzed biochemically with respect to storage materials, the primary and the secondary storage substances -- heparan sulfate and glycolipids, respectively. If time allows, histochemical study will also be performed to localize the differential accumulation of a variety of substrates in the brain. Generation of the mouse model for Sanfilippo B will be a valuable resource for the scientific community. It should be useful for future studies on the CNS degeneration in Sanfilippo syndrome and evaluation of therapies for the correction of this genetic disorder.