Cognate amino acid therapies provide preclinical benefit in 19 <i>C. elegans</i> models of ARS2 deficiency

Mitochondrial aminoacyl-tRNA synthetases (mt-ARS) are essential mitochondrial translation machinery components that catalyze mitochondrial transfer RNAs (tRNAs) charging with their cognate amino acid. Although mt-ARS have a common biochemical function, patients with mt-ARS pathogenic variants commonly develop neurological disorders with varying phenotypes, severity spectrum, and age of onset. Cognate amino acid supplementation has shown reported benefits in select cases of both mt-ARS ( <i>ARS2</i> ) and cytosolic ( <i>ARS1</i> ) deficiencies, although the safety and potential benefits of this candidate therapy approach across the full spectrum of mt-ARS disorders remain unclear. Here, <i>C. elegans</i> models were systematically generated for all 19 mitochondrial mt-ARS genes by feeding RNAi knockdown for one or two generations. mt-ARS deficient animals at baseline and upon cognate amino acid treatment were studied at the level of linear growth, neuromuscular activity, lifespan, mitochondrial physiology, and fertility. Results demonstrated that cognate amino acid treatment in a dose-dependent fashion consistently improved worm linear growth and neuromuscular activity, and reduced mitochondrial unfolded protein response stress, in all 19 knockdown models. It further rescued impaired fertility of <i>hars-1</i> and <i>fars-2</i> knockdown strains. Collectively, these preclinical studies provide compelling evidence to warrant future cognate amino acid treatment study in rigorous clinical trials spanning all human mt-ARS deficiencies.