[Mutations in aminoacyl-tRNA synthetase genes: an analysis of 10 cases]

Role of Mutations of Mitochondrial Aminoacyl-tRNA Synthetases Genes on Epileptogenesis

Mitochondria are the structures in cells that are responsible for producing energy. They contain a specific translation unit for synthesizing mitochondria-encoded respiratory chain components: the mitochondrial DNA (mt DNA). Recently, a growing number of syndromes associated with the dysfunction of mt DNA translation have been reported. However, the functions of these diseases still need to be precise and thus attract much attention. Mitochondrial tRNAs (mt tRNAs) are encoded by mt DNA; they are the primary cause of mitochondrial dysfunction and are associated with a wide range of pathologies. Previous research has shown the role of mt tRNAs in the epileptic mechanism. This review will focus on the function of mt tRNA and the role of mitochondrial aminoacyl-tRNA synthetase (mt aaRS) in order to summarize some common relevant mutant genes of mt aaRS that cause epilepsy and the specific symptoms of the disease they cause.

AARS2-Related Leukodystrophy: a Case Report and Literature Review

Mutations in the alanyl-transfer RNA synthase 2 (AARS2) represent a heterogenous group of autosomal recessive leukodystrophy characterized by cognitive decline, ataxia, spasticity, and Parkinsonism. AARS2-related leukodystrophy (AARS2-L) is extremely rare. To date, only 45 genetically confirmed cases, explaining the frequent diagnostic delay. Here, we report a 21-year-old male presented with unsteady gait and weakness in the bilateral lower extremities. Examination revealed dysarthria, cerebellar ataxia, paraparesis, and Parkinsonism with generalized hyperreflexia. MRI findings showed extensive white matter lesions in bilateral frontoparietal lobes, immediate periventricular regions, and corpus callosum. Focused exome sequencing revealed compound heterozygous mutations in the AARS2 gene confirming the diagnosis of AARS2-L; two heterogeneous missense mutations (c.452 T > C, p. M151T; c. 2557C > T, p. R853W) appeared together for the first time. We also reviewed phenotypic spectra of AARS2-related leukodystrophies from a total of 45 reported cases.