Translating Single-cell Vulnerability Into Novel ALS Biomarkers and Therapeutic Targets: Towards a Liquid Nerve Biopsy

The absence of specific biomarkers poses a significant impediment to the advancement of new treatments for amyotrophic lateral sclerosis (ALS), a severe and rapidly fatal neurodegenerative disease with no cure to date, defined by degeneration of motor neurons. Early pathological events, such as the selective damage of motor axons and the loss of neuromuscular connections, precede complete neurodegeneration and the manifestation of clinical symptoms. Therefore, we argue that understanding disease-related changes occurring in peripheral nerves is crucial for defining the underlying pathogenetic mechanisms. Preliminary data from our research team suggest that phosphorylated TDP-43, the pathological hallmark of ALS, forms aggregates in motor axons and Schwann cells of living ALS patients before the onset of axonal degeneration. However, peripheral nerves constitute complex multicellular tissues, and the specific contributions of individual cellular components to ALS pathology remain poorly understood. The overarching concept of this proposal is that distinct cell types within the nerve tissue (e.g., Schwann cells, endothelial cells, fibroblasts, macrophages) function as exquisite early detectors of motor neuron damage and initiate secondary responses that amplify neuropathology. These studies will steer the analysis of minimally invasive skin biopsies to uncover deregulated PNS signatures in ALS patients. Finally, candidate molecular targets reflecting cell-type-specific deregulation in the diseased nerve microenvironment will be screened in the biofluids of ALS patients and at-risk individuals from genetic ALS families, enabling the discovery of novel diagnostic and prognostic biomarkers. The integrative approach proposed in this study will elucidate the pathogenic mechanisms of ALS and establish a roadmap towards identifying potential therapeutic targets.