The+Tay+Sachs+Disease

hexosaminidase A (alpha polypeptide)





Nature of the Genetic Difficulty
Tay Sachs disease is an autosomal recessive genetic disorder which results from a mutation that occur on the HEXA gene which is located between base pairs 70,422,832 and 70,455,392 on chromosome 15 (15q23-q24). Tay Sachs disease can result from various types of mutations such as base pair insertions, base pair deletions, splice site mutations, and point mutations. In total, scientists have been able to identify more than 120 different mutations on the HEXA gene that cause Tay Sachs disease.

Basis Facts of Disease
When Tay Sachs disease occurs it reduces or eliminates the activity of beta-hexosaminidase A. This enzyme is found in lysomes (cellular structures that break down toxix substances) and responsible for breaking down GM2 gangliosides (fatty substances in brain and nerve cells). As a result of the bodies inabilty to break down the GM2 gangliosides, the fatty substances build up in the cells. As the gangliosides build up to toxic levels, progressive damage occurs at which point the body has no choice but to destroy the cells altogether and the signs and symptoms of Tay Sachs disease are displayed.

Tay Sachs disease is more commonly found in infants who progress normally until they are between 6 and 10 months old.

Tay Sachs patients have a cherry red spot in the back of their eyes visible through an ophthalmoscope and the first symtoms that occur are usually twichting in the eyes. The babies then lose their ability to crawl, drink and sit up. Eventualy they can become blind, deaf, paralysized and have siezures before dying.

Prognosis
Infantile acute form: Shows up between 6-10 months. Children usually die by the time they are 5 years old.

Late infantile and juvenile subacute form: Shows up when child is between 2-10 years old and children usually die by the time they are 15.

Adult chronic form: Shows up in childhood and adulthood and patients have much higher chances of living and don't usually die.

Scientist are looking at enzyme replacement therapy, gene therapy and substrate reduction therapy as possible treatments but they are still in the experimental stages. The treatments that do exist are not cures and do not help very much in extending patient's life-span.

Sources Cited
http://www.diseaseaday.com/brain/the-grey-corner-tay-sachs-disease-fat-accumulating-in-the-brain

http://www-personal.umd.umich.edu/~jcthomas/JCTHOMAS/1997%20Case%20Studies/S.%20Bergeron.html

http://ghr.nlm.nih.gov/gene=hexa