sacsin molecular chaperone
The SACS gene provides instructions for producing a protein called sacsin. Sacsin is found in the brain, skin cells, muscles used for movement (skeletal muscles), and at low levels in the pancreas, but the specific function of the protein is unknown. Research suggests that sacsin may play a role in folding newly produced proteins into the proper 3-dimensional shape because it shares similar regions with other proteins that perform this function.
Approximately 28 mutations in the SACS gene have been found to cause autosomal recessive spastic ataxia of Charlevoix-Saguenay, commonly called ARSACS. Two mutations have been found frequently in affected people from Quebec. One of these mutations deletes a DNA building block (nucleotide) called thymine at position 6594 in the SACS gene (written as 6594delT). This mutation is found in more than 90 percent of people with ARSACS in Quebec. The other mutation replaces the nucleotide cytosine with the nucleotide thymine at position 5254 in the SACS gene (written as C5254T). Both of these mutations lead to production of a sacsin protein that is abnormally short and nonfunctional. Mutations causing ARSACS in people outside of Quebec are varied and usually unique to that person or family. Most of these mutations either delete one or more nucleotides or replace one nucleotide with another nucleotide in the SACS gene. Mutations in the SACS gene cause the production of an unstable sacsin protein that does not function normally. It is unclear how the abnormal sacsin protein affects the brain and skeletal muscles and results in the signs and symptoms of ARSACS.
- spastic ataxia of Charlevoix-Saguenay (sacsin)