What is the official name of the HEXA gene? The official name of this gene is hexosaminidase A (alpha polypeptide). HEXA is the gene's official symbol. The HEXA gene is also known by other names, listed below. What is the normal function of the HEXA gene? The HEXA gene instructs cells to make one part of an enzyme called beta-hexosaminidase A. Specifically, the HEXA gene makes the alpha subunit of this enzyme. One alpha subunit comes together with one beta subunit (made by the HEXB gene) to form a functioning enzyme. Beta-hexosaminidase A is found in lysosomes, which are structures in cells that break down toxic substances and act as the cell's recycling center. Within lysosomes, beta-hexosaminidase A forms part of a complex that breaks down a fatty substance called GM2 ganglioside. What conditions are related to the HEXA gene? Tay-Sachs disease - caused by mutations in the HEXA gene More than 95 mutations that cause Tay-Sachs disease have been identified in the HEXA gene. These mutations reduce or eliminate the activity of the enzyme beta-hexosaminidase A, preventing the normal breakdown of GM2 ganglioside in the brain and spinal cord. As a result, this substance builds up to toxic levels in nerve cells. Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these cells, which causes the signs and symptoms of Tay-Sachs disease. About 70 of the known mutations in the HEXA gene lead to a completely nonfunctional version of beta-hexosaminidase A. These mutations cause the severe form of Tay-Sachs disease, which begins in infancy. Other mutations, which reduce but do not eliminate the activity of beta-hexosaminidase A, are responsible for the less severe forms of Tay-Sachs disease that appear later in life.