The accumulation of cellular damage, including DNA damage, is hypothesized to contribute to aging-related neurodegenerative changes. DNA excision repair crosscomplementing group 1 (Ercc1) knock-out mice represent an accepted model of neuronal aging, showing gradual neurodegenerative changes, including loss of synaptic contacts and cell body shrinkage. Here, we used the Purkinje cell-specific Ercc1 DNA-repair knockout mouse model to study aging in the mouse cerebellum. We performed an in-depth quantitative proteomics analysis, using stable isotope dimethyl labeling, to decipher changes in protein expression between the early (8 weeks), intermediate (16 weeks), and late (26 weeks) stages of the phenotypically aging Ercc1 knock-out and healthy littermate control mice. The expression of over 5,200 proteins from the cerebellum was compared quantitatively, whereby 79 proteins (i.e. 1.5%) were found to be substantially regulated during aging. Nearly all of these molecular markers of the early aging onset belonged to a strongly interconnected network involved in excitatory synaptic signaling. Using immunohistological staining, we obtained temporal and spatial profiles of these markers confirming not only the proteomics data but in addition revealed how the change in protein expression correlates to synaptic changes in the cerebellum. In summary, this study provides a highly comprehensive spatial and temporal view of the dynamic changes in the cerebellum and Purkinje cell signaling in particular, indicating that synapse signaling is one of the first processes to be affected in this premature aging model, leading to neuron morphological changes, neuron degeneration, inflammation, and ultimately behavior A link between DNA damage and the process of aging has been firmly established (1, 2). The brain in particular is a vulnerable organ that is plagued by various neurodegenerative disorders that have been related to aging, i.e. Alzheimer and Parkinson disease. The study of the early onset of agerelated neurodegenerative diseases is challenging, because there are not many confident early molecular determinants that predict their development. Therefore, progeroid syndromes (showing premature aging) are often used as a model for segmental aging as they show consistent and predictive elements of the aging phenotype (e.g. cessation of growth and development, hearing loss, and severe and progressive neuron dysfunction) (1, 3). These accelerated aging syndromes have in common that they carry defects in one or multiple proteins involved in DNA damage repair mechanisms.A well established progeroid mouse model is the excision repair cross-complementing group 1 (Ercc1) 1 gene knock-out (4, 5). The Ercc1-xeroderma pigmentosum group F complex acts as a nuclease in the nucleotide excision repair pathway and has an important function in both global genome and transcription-coupled DNA damage repair. Besides its role in nucleotide excision repair, Ercc1 is also involved in interstrand cross-link repair and oxidative damage repair. The accum...