Modelling the Role of Mitochondrial Aspartyl-tRNA Synthetase (DARS2) in Neurodegeneration

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Mitochondrial dysfunction, whether primary or secondary, is increasingly recognized as a central feature of neurodegeneration. The increasing prevalence of these diseases in our ageing populations means that understanding the mechanisms behind mitochondrial involvement in neuronal loss is a pressing public health issue. Recently, the autosomal recesive leucencephalopathy with brainstem and spinal cord involvement and lactacidosis syndrome (LBSL) is added to a large group of mitochondrial disorders. The disorder, clinically characterized by slowly progressive cerebellar ataxia, spasticity and dorsal column dysfunction, is caused by mutations in the DARS2 gene, which encodes for the mitochondrial aspartyl tRNA synthetase. Remarkably, mutations in other mitochondrial tRNA synthetase genes give rise to disorders with a very tissue specific pattern, despite primary function of all these genes in the protein synthesis within mitochondria. Our project will employ innovative and novel cell and animal models to elucidate the mechanisms of neurodegeneration caused by DARS2 mutations and use the findings to decipher a possible role of tissue specificity of mitochondrial diseases. We will focus our efforts to answer specific questions: (i) What is the cellular and tissue pathogenesis associated with DARS2 deficiency in forebrain neurons and white matter? (ii) What are the mechanisms whereby DARS2 deficiency impacts mitochondrial proficiency in vivo? (iii) What is the basis for the exquisite sensitivity of neurons to specific DARS2 missense mutations found in LBSL patients? We will address these questions by analysing DARS2 deficiency in forebrain neurons and white matter specific knockout mouse models we already produced. We will also introduce the most common missense mutations found in patients in different neuronal, neural and non-neural cell lines and analyze their impact in on mitochondrial and cellular function. Finally, we propose to use novel CRISPR/Cas9 technology to generate a mouse model carrying the most common DARS2 missense mutation found in patients to most accurately model the LBSL in vivo. We believe that an integrative approach combining animal models with different mammalian cells will make a greater impact on the understanding of the role of mitochondrial dysfunction in neurodegeneration.