What Is Tay-Sachs Disease?
Tay-Sachs disease is a rare and fatal inherited genetic disorder that causes a progressive build-up of a fatty substance in the nerve cells (neurons) of the brain and spinal cord because of a defect in a gene called HEXA. The most common form of the disease strikes in infancy. Affected infants appear healthy at birth, but by 3 to 6 months of age they begin to weaken and lose motor skills, and they develop an exaggerated startle reaction to loud noises. As the disease progresses, neurological impairment increases, causing seizures and paralysis. These children rarely live past the age of 4 years. Less common forms of the disease that first show symptoms later (juvenile- and adult-onset) also occur and progression of the neurological impairment, while still severe, is generally slower than the infantile-onset form.
Why Is the HEXA Gene Important?
The HEXA gene produces an enzyme called ß-hexosaminidase A, which plays critical role in breaking down a fatty substance called GM2 ganglioside in the central nervous system. Mutations in the HEXA gene disrupt production of the ß-hexosaminidase A enzyme, resulting in a toxic build-up of the GM2 ganglioside in the cells of the central nervous system.
How Is Tay-Sachs Disease Inherited?
Tay-Sachs disease is a recessive condition, meaning that an affected individual must have two defective copies of the gene: one from each parent. The parents are carriers, but don’t have the disease themselves.
How Common Is Tay-Sachs Disease?1, 2
Tay-Sachs is a rare disease. In the general population, approximately 1 person in 250 is a carrier for Tay-Sachs disease. However, certain population groups have a higher incidence. In people of Ashkenazi Jewish descent, it’s estimated that 1 person in 27 is a carrier. People of Irish descent, the French Canadian community in the eastern St. Lawrence River Valley, and the Cajun community in Louisiana are among those groups identified with a higher prevalence of carriers. Nevertheless, Tay-Sachs disease is found across all racial, ethnic and religious populations worldwide.
What Can Be Done?
The availability of carrier screening and prenatal testing has decreased the incidence of Tay-Sachs disease in populations known to have a high risk for the disease. But babies with Tay-Sachs disease continue to be born to parents not known to be carriers.
There is currently no cure for Tay-Sachs disease. In the more common infantile- and the juvenile-onset forms of the disease, treatment is currently limited to management of symptoms and support. In the less severe adult-onset form, some preliminary success has been seen using molecular chaperone therapy, where a chemical treatment is used to protect the enzyme ß-hexosaminidase A3.
One of the most promising avenues of research is gene therapy. Gene therapy is complex, but the idea is to find a way of “packaging” a correct version of the defective gene (HEXA in the case of Tay-Sachs disease) so that it can be delivered into the affected cells (nerve cells in the central nervous system in the case of Tay-Sachs disease), much like a patch in the case of faulty software. The goal would be for the correct gene to become functional and permanently incorporated into the affected cells.
Where Does the BLU GENES Foundation Fit In?
Tay-Sachs disease and most other diseases that are potentially treatable with gene therapy are rare. They lack visibility and the funding support available for more common diseases. But we know that the parents of a baby diagnosed with Tay-Sachs disease don’t care how rare it is, and we know they need hope.
The BLU GENES Foundation is raising funds to advance gene therapy and find a cure for genetic disorders, beginning with Tay-Sachs disease. We believe in offering hope where currently there is none.
- The website for the World Health Organization; search “Tay-Sachs disease” and select “Genes and human disease” http://www.who.int/genomics/public/geneticdiseases/en/index2.html#ts
- The website for the National Center for Biotechnology Information; “Books” database; GeneReviews, “Hexosaminidase A Deficiency”; Kaback, Michael M. and Desnick, Robert J.; last update August 11, 2011. https://www.ncbi.nlm.nih.gov/books/NBK1218/
- The website for the National Tay-Sachs and Allied Diseases Association; “Research Guide for Families”; Research by Disease; Tay-Sachs Disease
You can help by making a tax-deductible donation to advance gene therapy now.