SLC52A3

The SLC52A3 gene (previously called the C20orf54 gene) provides instructions for making the riboflavin transporter 2 (RFT2) protein. This protein transports a vitamin called riboflavin (or vitamin B₂) across the cell membrane. Riboflavin cannot be made by the body, so it must be obtained from the food a person eats. The RFT2 protein is found at especially high levels in cells of the small intestine and is important for absorbing riboflavin from the small intestine after digestion so that the vitamin can be used in the body.

Riboflavin is the core component of molecules called flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These molecules function as coenzymes, which means they help enzymes carry out chemical reactions. FAD and FMN are involved in many different chemical reactions and are required for a variety of cellular processes. One important role of these coenzymes is in the production of energy for cells. FAD and FMN are also involved in the breakdown (metabolism) of carbohydrates, fats, and proteins.

Brown-Vialetto-Van Laere syndrome - caused by mutations in the SLC52A3 gene

Mutations in the SLC52A3 gene can cause Brown-Vialetto-Van Laere syndrome (BVVLS), a neurological condition characterized by nerve paralysis, hearing loss, muscle weakness, and breathing problems. The gene mutations involved in this condition lead to an abnormal RFT2 protein with impaired ability to transport riboflavin. Consequently, there is a reduction of riboflavin available in the body. However, it is unclear how these changes lead to the nerve problems characteristic of BVVLS.

other disorders - caused by mutations in the SLC52A3 gene

Mutations in the SLC52A3 gene are involved in a condition similar to Brown-Vialetto-Van Laere syndrome (BVVLS, discussed above) called Fazio-Londe disease. People with this condition have signs and symptoms similar to those of BVVLS but without hearing loss. Typically, people with Fazio-Londe disease have breathing problems, drooping eyelids (ptosis), and muscle weakness in the face and limbs, which worsen rapidly. As in BVVLS, mutations in the SLC52A3 gene that cause Fazio-Londe disease impair the absorption of riboflavin from the small intestine. Some researchers believe that these disorders are not two separate conditions; instead, they are forms of a single disorder with varying signs and symptoms.