SLC25A4

The SLC25A4 gene provides the instructions for making a protein called adenine nucleotide translocase type 1 (ANT1). ANT1 functions in mitochondria, which are structures within cells that convert the energy from food into a form that cells can use. This process, called oxidative phosphorylation, converts adenosine diphosphate (ADP) into adenosine triphosphate (ATP), the cell's main energy source. ANT1 forms a channel in the mitochondrion's inner membrane. This channel allows ADP into the mitochondrion and ATP out of the mitochondrion to be used as energy for the cell. ANT1 may also be a part of another structure in the inner membrane called the mitochondrial permeability transition pore. This structure allows various molecules to pass into the mitochondrion and is thought to play a role in the self-destruction (apoptosis) of the cell.

progressive external ophthalmoplegia - caused by mutations in the SLC25A4 gene

At least five mutations in the SLC25A4 gene have been reported to cause an eye condition called progressive external ophthalmoplegia. This disorder weakens the muscles that control eye movement and causes the eyelids to droop (ptosis). However, the role mutated ANT1 plays in causing the condition is not well understood.

Mitochondria each contain a small amount of DNA, known as mitochondrial DNA (mtDNA), which is essential for the normal function of these structures. Although the mechanism is unclear, mutations in the SLC25A4 gene result in large deletions of genetic material from mtDNA in muscle tissue. Researchers have not determined how deletions of mtDNA lead to the specific signs and symptoms of progressive external ophthalmoplegia, although the features of the condition are probably related to impaired oxidative phosphorylation. It has been suggested that eye muscles are commonly affected by mitochondrial defects because they are especially dependent on oxidative phosphorylation for energy.