Proteomic analysis of brain and spinal cord tissue reveals distinct immune and mitochondrial processes between human...

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease resulting in the progressive loss of motor neurons in the brain and spine. More than 95% of cases are pathologically characterized by the cytoplasmic accumulation of hyperphosphorylated and ubiquitinated transactive response DNA-binding protein 43 (TDP-43). Multiple mouse models with TDP-43 accumulation have been developed, however, whether they recapitulate molecular features of ALS pathology is unclear. Given the lack of curative treatment for ALS, there is an urgent need to identify the precise biological processes contributing to disease pathogenesis for the development of effective therapeutic treatments. Thus, in this study we employed label-based untargeted proteomics to characterize the ALS proteome and related biological processes in the spinal cord and brain of TDP-43^Q331K mice, a transgenic mouse model of ALS and the motor cortex and the cervical, thoracic, and lumbar spinal cord regions from humans. In humans, we observed highly overlapping responses across the four tissues examined, primarily related to the upregulation of immune processes and the downregulation of mitochondrial function. In contrast, TDP-43^Q331K mice demonstrate a lack of enrichment for immune activation and the opposite regulation of mitochondrial processes. A meta-analysis of previously published mouse datasets identified the Ubqln2 knock-out mouse model as showing stronger parallels with our late-stage human ALS. Overall, this study provides in-depth analysis of the site-specific dysregulated proteomes and their associated functional processes across species. Thereby, identifying potential therapeutic targets while emphasizing the limitations of specific mouse models at certain timepoints in recapitulating ALS-related processes for future model development.