No description available.

Tay-Sachs and Sandhoff diseases are autosomal recessive disorders of GM2 ganglioside catabolism resulting from deficient activity of lysosomal beta-hexosaminidase A (Hex A) or Hex A and Hex B, respectively. This leads to a massive and fatal accumulation of GM2 ganglioside in the neurons of affected patients. Mouse models of Tay-Sachs and Sandhoff diseases, created via targeted disruption of the Hexa and Hexb genes, revealed that while Hexb -/- mice suffer a profound, fatal neurodegenerative disease as expected, Hexa -/- mice escape disease to about one year. This protection is conferred by an ability to degrade GM2 ganglioside by means of a lysosomal sialidase mediated metabolic bypass. To determine if such a bypass could be made to function in humans, a series of experiments were performed to examine and compare the activity of mouse and human lysosomal sialidases in their ability to promote GM2 catabolism. The results suggest that human lysosomal sialidase, though sluggish, can indeed degrade GM2 when induced sufficiently.

No description available.

No description available.

GM$ sb2$ ganglioside hydrolysis requires the formation of a ternary complex consisting of substrate, enzyme ($ beta$-N-acetylhexosaminidase A = Hex A), and the GM$ sb2$ activator protein. In order to study the interaction between Hex A and GM$ sb2$ activator, the human GM$ sb2$ activator cDNA was cloned into the p-FLAG vector. The fusion protein (FLAG-AP) was expressed in E. coli, and purified to homogeneity using immunoaffinity chromatography. / A retardation assay was designed using the immunoaffinity column to detect transient interactions between FLAG-AP and Hex A. Hex A and Hex S are retarded by the column, but not Hex B or unrelated proteins. Hex A retardation is absolutely dependent upon the presence of immobilized FLAG-AP, but does not require the presence of GM$ sb2$ ganglioside. Interaction of GM$ sb2$ activator and Hex A does not involve the enzyme's active site, but does appear to depend upon hydrophobic interactions between the two proteins.

No description available.

This thesis describes a search for DNA polymorphisms at the HEXA locus as well as the characterization of three Tay-Sachs disease (TSD) mutations in the Chinese population. / No polymorphisms were detected in the HEXA gene by three different methods: (1) Southern blotting; (2) PCR amplification and restriction enzyme digestion of intronic sequences; (3) single strand conformational polymorphism (SSCP) analysis of introns. The apparent deficiency of accessible polymorphisms is a handicap in studying the origin, distribution, and frequency of mutant HEXA alleles in human populations. / I have characterized five of six infantile TSD alleles segregating in three unrelated Chinese families in which there is no known consanguinity. Two of the mutations described are novel, the third is a transition previously reported in an Italian patient (Nakano et al, 1988). / The two novel mutations occur in homozygous form in the affected individuals investigated. They are: (1) an insertion of an A at nucleotide 547 (Family 1) and (2) a T1453C transition (Family 2). (Abstract shortened by UMI.)

No description available.

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