Aspartyl-tRNA Synthetase 2, Mitochondrial: The DARS2 gene provides instructions for making an enzyme called mitochondrial aspartyl-tRNA synthetase.
This enzyme is important in the production (synthesis) of proteins in cellular structures called mitochondria, the energy-producing centers in cells. While most protein synthesis occurs in the fluid surrounding the nucleus (cytoplasm), some proteins are synthesized in the mitochondria.
During protein synthesis, in either the mitochondria or the cytoplasm, a type of RNA called transfer RNA (tRNA) helps assemble protein building blocks (amino acids) into a chain that forms the protein. Each tRNA carries a specific amino acid to the growing chain. Enzymes called aminoacyl-tRNA synthetases, including mitochondrial aspartyl-tRNA synthetase, attach a particular amino acid to a specific tRNA. Mitochondrial aspartyl-tRNA synthetase attaches the amino acid aspartic acid to the correct tRNA, which helps ensure that aspartic acid is added at the proper place in the mitochondrial protein.
At least 25 mutations in the DARS2 gene have been identified in people with leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL), a condition that affects the brain and spinal cord and causes difficulty walking. The most common mutation that causes this condition disrupts the way genetic information is pieced together to make a blueprint for producing the mitochondrial aspartyl-tRNA synthetase enzyme. Most copies of the blueprint are pieced together incorrectly, which prevents the enzyme from being produced. However, some copies are pieced together correctly, and a small amount of normal enzyme is made. Other mutations change single amino acids in the enzyme. This type of mutation results in decreased mitochondrial aspartyl-tRNA synthetase enzyme activity. With reduced activity, the enzyme has difficulty adding aspartic acid to the tRNA, which hinders the addition of this amino acid to mitochondrial proteins.
It is unclear how the gene mutations lead to the signs and symptoms of LBSL. Researchers do not understand why reduced activity of mitochondrial aspartyl-tRNA synthetase specifically affects certain parts of the brain and spinal cord.
aspartate tRNA ligase 2, mitochondrial
aspartyl-tRNA synthetase, mitochondrial
aspartyl-tRNA synthetase, mitochondrial precursor