LiBi-NMD: liquid biopsies in neuromuscular diseases - the underrated value of white blood cells

Biochemical, histological, and ultra-structural studies are standard procedures in the diagnostic work-up of muscle and nerve biopsies derived from neuromuscular patients and moreover represent important biomedical research approaches toward a better understanding of the etiology of neuromuscular diseases (NMDs). In the era of next-generation-sequencing approaches, evaluation of the pathogenicity of genetic variants on muscle and nerve biopsies is often crucial. However, the investigation of tissue biopsies also harbours significant limitations: sampling is invasive, amount of tissue is often limited, and biopsies can only provide a snapshot of the disease at a given timepoint. Repeated biopsy sampling is not an option to monitor disease progression on a cellular level. Previous studies on certain diseases have already occasionally emphasized the potential of white blood cells (WBC) in the diagnostics and research of NMDs. This prompted us to initiate LiBi-NMD, a project systematically addressing the value of WBC in terms of liquid biopsies to study the etiology of neuromuscular diseases on a cellular level but in a minimal-invasive manner. By using mass spectrometry, we catalogued 211 out of 379 proteins (55.7%) linked to the manifestation of a NMD (covering peripheral nervous system diseases, myasthenic syndromes and myopathies) in WBC and provide information regarding their dynamics during aging. By electron microscopy, proteomics, high-dimensional cytometry and immunoblotting, we demonstrated their potential to (i) recapitulate ultra-structural perturbations usually detected in muscle biopsies, (ii) evaluate the pathogenicity of ambiguous variants, (iii) identify disease-relevant pathophysiological processes (paradigmatically shown for GAN- and SH3TC2-related neuropathies & ANO5- and CAPN3-related myopathies), and to (iv) monitor the biochemical fingerprint of disease progression (paradigmatically shown for myasthenic syndromes). Additionally, we highlight their potential to (v) monitor the success of intervention concepts in terms of the definition of cellular but minimally-invasive therapy markers. Biochemical, histological, and ultra-structural studies are standard procedures in the diagnostic work-up of muscle and nerve biopsies derived from neuromuscular patients and moreover represent important biomedical research approaches toward a better understanding of the etiology of neuromuscular diseases (NMDs). In the era of next-generation-sequencing approaches, evaluation of the pathogenicity of genetic variants on muscle and nerve biopsies is often crucial. However, the investigation of tissue biopsies also harbours significant limitations: sampling is invasive, amount of tissue is often limited, and biopsies can only provide a snapshot of the disease at a given timepoint. Repeated biopsy sampling is not an option to monitor disease progression on a cellular level. Previous studies on certain diseases have already occasionally emphasized the potential of white blood cells (WBC) in the diagnostics and research of NMDs. This prompted us to initiate LiBi-NMD, a project systematically addressing the value of WBC in terms of liquid biopsies to study the etiology of neuromuscular diseases on a cellular level but in a minimal-invasive manner. By using mass spectrometry, we catalogued 211 out of 379 proteins (55.7%) linked to the manifestation of a NMD (covering peripheral nervous system diseases, myasthenic syndromes and myopathies) in WBC and provide information regarding their dynamics during aging. By electron microscopy, proteomics, high-dimensional cytometry and immunoblotting, we demonstrated their potential to (i) recapitulate ultra-structural perturbations usually detected in muscle biopsies, (ii) evaluate the pathogenicity of ambiguous variants, (iii) identify disease-relevant pathophysiological processes (paradigmatically shown for GAN- and SH3TC2-related neuropathies & ANO5- and CAPN3-related myopathies), and to (iv) monitor the biochemical fingerprint of disease progression (paradigmatically shown for myasthenic syndromes). Additionally, we highlight their potential to (v) monitor the success of intervention concepts in terms of the definition of cellular but minimally-invasive therapy markers.