AARS2 and Leukoencephalopathy: DARS2, encoding the mitochondrial aspartyl-tRNA synthetase (mt-AspRS), was the first aaRS2 gene reported to cause a human disease, characterized by a peculiar leukoencephalopathy named LBSL (leukoencephalopathy with brain stem and spinal cord involvement, OMIM #611105) [21] associated with cerebellar ataxia, spasticity, and variable degree of cognitive impairment.