New Therapeutic Avenue for ALS: Avoiding a Fatal Encounter of TDP-43 at the Mitochondria

Impairment of mitochondrial oxidative phosphorylation in skin fibroblasts of SALS and FALS patients is rescued by in vitro treatment with ROS scavengers

Amyotrophic lateral sclerosis (ALS) is a devastating, rapidly progressive, neurodegenerative disorder affecting upper and lower motor neurons. Approximately 10% of patients suffer from familial ALS (FALS) with mutations in different ubiquitously expressed genes including SOD1, C9ORF72, TARDBP, and FUS. There is compelling evidence for mitochondrial involvement in the pathogenic mechanisms of FALS and sporadic ALS (SALS), which is believed to be relevant for disease. Owing to the ubiquitous expression of relevant disease-associated genes, mitochondrial dysfunction is also detectable in peripheral patient tissue. We here report results of a detailed investigation of the functional impairment of mitochondrial oxidative phosphorylation (OXPHOS) in cultured skin fibroblasts from 23 SALS and 17 FALS patients, harboring pathogenic mutations in SOD1, C9ORF72, TARDBP and FUS. A considerable functional and structural mitochondrial impairment was detectable in fibroblasts from patients with SALS. Similarly, fibroblasts from patients with FALS, harboring pathogenic mutations in TARDBP, FUS and SOD1, showed mitochondrial defects, while fibroblasts from C9ORF72 associated FALS showed a very mild impairment detectable in mitochondrial ATP production rates only. While we could not detect alterations in the mtDNA copy number in the SALS or FALS fibroblast cultures, the impairment of OXPHOS in SALS fibroblasts and SOD1 or TARDBP FALS could be rescued by in vitro treatments with CoQ₁₀ (5 μM for 3 weeks) or Trolox (300 μM for 5 days). This underlines the role of elevated oxidative stress as a potential cause for the observed functional effects on mitochondria, which might be relevant disease modifying factors.

Editing the Epigenome: Reshaping the Genomic Landscape

The eukaryotic epigenome has an instrumental role in determining and maintaining cell identity and function. Epigenetic components such as DNA methylation, histone tail modifications, chromatin accessibility, and DNA architecture are tightly correlated with central cellular processes, while their dysregulation manifests in aberrant gene expression and disease. The ability to specifically edit the epigenome holds the promise of enhancing understanding of how epigenetic modifications function and enabling manipulation of cell phenotype for research or therapeutic purposes. Genome engineering technologies use highly specific DNA-targeting tools to precisely deposit epigenetic changes in a locus-specific manner, creating diverse epigenome editing platforms. This review summarizes these technologies and insights from recent studies, describes the complex relationship between epigenetic components and gene regulation, and highlights caveats and promises of the emerging field of epigenome editing, including applications for translational purposes, such as epigenetic therapy and regenerative medicine.