Protein signature of human white blood cells enables biochemical tracking of rare neurological diseases

Abstract Background: The identification of pathomechanisms leading or contributing to the clinical manifestation of rare neurological diseases such as neuromuscular diseases (NMD) is crucial. The study of the molecular basis of these diseases is also important for the definition of starting points for (new) therapeutic intervention concepts as well as for testing of pathogenicity of genetic variants identified by sequencing approaches. However, these studies are frequently limited by the availability of human biomaterial. Methods: Human white blood cells were used to generate a spectral library using pH8-fractionation followed by nano liquid chromatography coupled to tandem mass spectrometry. To demonstrate the suitability of this approach, we next subjected proteins isolated from white blood cells derived from two CHKB patients to a data independent acquisition approach. Paradigmatic proteomic findings were confirmed by immunofluorescence in a muscle biopsy derived from one of these patients.Results: To investigate if human white blood cells might serve as valuable biomaterial for (molecular) studies of NMD, we generated a protein library cataloguing 7543 proteins covering 52.2 % of proteins for which mutations in corresponding genes are known to be causative for NMDs. Based on these findings, we aimed to further demonstrate the suitability of this in vitro model to study the etiopathology of a rare NMD caused by bi-allelic variants within CHKB. Dysregulation of paradigmatic proteins could be confirmed in the quadriceps muscle biopsy of one of these patients and protein-functions provided new insights into the underlying pathophysiology indicating affection of subcellular structures (functionally) connected to mitochondria such as the Endoplasmic Reticulum (ER) and cytoskeleton. Moreover, altered protein clearance is indicated by our combined proteomic and immunofluorescence findings.Conclusions: Our combined data reveal that human white blood cells may serve as an in vitro system to study the molecular etiology of rare neurological diseases exemplified on a rare mitochondrial NMD based on pathogenic variants affecting CHKB in an unbiased fashion.