What Is Tay-Sachs Disease? - Symptoms and Genetic Cause

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  • 0:05 What is Tay-Sachs Disease?
  • 1:05 Genetics of Tay-Sachs Disease
  • 1:17 Biochemistry of…
  • 2:35 Progression of…
  • 3:19 Lesson Summary
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Lesson Transcript
Instructor: Joshua Anderson
Tay-Sachs is a devastating genetic disorder that is seen in infants starting when they are only three to six months old. Children who suffer from this disease usually die by the age of four. Learn more about the symptoms and genetic causes of this autosomal recessive disorder.

What is Tay-Sachs Disease?

Today we're going to talk about Tay-Sachs disease. So let's start with the question 'What is Tay-Sachs disease?' Tay-Sachs disease is a rare genetic disorder in humans that causes progressive neurological deterioration starting at only three to six months of age. Sadly, there is no known cure or effective treatment for Tay-Sachs disease, and most children who suffer from the disease die by the age of four. So why is Tay-Sachs disease so devastating and so deadly? The answers to these questions can be found by studying the genetics and biochemistry that cause the disease in the first place.

Genetics of Tay-Sachs Disease

Tay-Sachs disease is an autosomal recessive disorder, which, you may remember, means that it is a genetic disorder that is caused by a gene on an autosome and is only seen in individuals with two copies of the affected allele. Tay-Sachs disease is caused by mutations of the HEXA gene, and an affected individual must receive copies of the disease allele from both parents.

Biochemistry of Tay-Sachs Disease

The HEXA gene encodes an enzyme called beta-hexosaminidase A, which is an enzyme necessary for the normal degradation of GM2 ganglioside. The Tay-Sachs mutations are severe and cause cells to make dysfunctional enzyme with no biochemical activity. In the developing brain of a young child, GM2 ganglioside is rapidly made and degraded.

If the child doesn't have any beta-hexosaminidase A activity because both copies of their HEXA genes are producing dysfunctional enzymes, then GM2 ganglioside builds up in the neurons and eventually destroys them. Because they don't have any functional beta-hexosaminidase A enzyme in their neurons, individuals with Tay-Sachs disease cannot clear the excess GM2 ganglioside.

Finding a treatment for Tay-Sachs disease has proven very difficult because nobody has yet found a good method of clearing excess molecules or replacing enzymes within cells. Hopefully one day, gene therapy or some other treatment will be able to address these problems and cure this disease.

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