Tay-Sachs Essays -- Health Medical Medicine Biology Essays

Tay-Sachs Abstract Tay-Sachs is a disease caused by a mutation to the gene which codes for Hex A. Without Hex A, a cell cannot degrade GM2 ganglioside into GM3 ganglioside. This results in a build up of ganglioside’s in lysosomes of neurons. The result is varying degrees of mental deterioration. New DNA-based screening is currently being developed to replace the enzyme-based screening techniques that have been used since 1969. This will not only speed up the diagnosis, but also allow for earlier detection of Tay-Sachs by using the parents genotypes. Introduction Tay-Sachs disease is one of three autosomal recessive, lysosomal storage disorders, collectively known as the GM2 gangliosidoses. They result from accumulation of GM2 ganglioside in lysosomes, primarily of neurons. The clinical symptoms of Tay-Sachs vary from infantile lethal neurodegenerative disease to less severe adult onset forms. The latter are often characterized by motor neuron impairments. The recognition of the high incidence of this disease among Ashkenazi Jews and the identification of the deficiency of hexosaminidase A as the basic defect were essential findings leading to the establishment of mass carrier screening programs for this disease [2]. Recently, research has focused on the DNA-based diagnostics that are anticipated to play a role in future carrier screening programs [1]. GM2 ganglioside hydrolysis The lysosomal hydrolase, beta-hexosaminidase, occurs predominantly in two forms, hexosaminidase A (Hex A) and hexosaminidase B (Hex B). Hex A is comprised of one alpha and one beta subunit while Hex B is comprised of two beta subunits [3]. While both subunits contain similar active sites, only the alpha subunit can hydrolyze GM2 gan... ... Gravel, R. (1990). The molecular basis of Tay-Sachs disease: mutation identification and diagnosis. Clin. Biochem. 23:409-415. 2. Navon, R., Proia, R. (1991). Tay-Sachs disease in Moroccan Jews deletion of a phenylalanine in the alpha-subunit of beta--hexosaminidase. Am. J. Hum. Genet. 48:412-419. 3. Gray, R.G.F., Green, A., Rabb, L., Broadhead, D.M., Besley, G.T.N. (1990). A case of the B1 variant of GM2-gangliosidosis. J. Inher. Metab. Dis. 13:280-282. 4. Meier, E., Schwarzmann, G., Furst, W., Sandhoff, K. (1991). The human GM2 activator protein. J. Biological Chem. 266:1879-1887. 5. Mahuran, D.J. (1991). The biochemistry of HEXA and HEXB gene mutations causing GM2 gangliosidosis. Biochimica et Biophysica Acta. 1096:87-94. 6. Robbins, S., Ranzi, R., Kumar, V., (Eds). (1984). Pathologic Basis of Disease. Philadelphia, PA: Saunders Co. 142-145.