Comprehensive histomorphological and molecular mapping of the normal adult mouse cerebellum as a physiological baseline for ataxia-telangiectasia research

Ataxia-Telangiectasia (A-T) is a progressive neurodegenerative disorder caused by mutations in the ATM gene, primarily affecting the cerebellum and leading to severe motor impairment. While the role of ATM in DNA repair is well established, its influence on the broader histomorphological and molecular landscape of cerebellar homeostasis remains less understood. This study aims to establish a comprehensive physiological map of key signaling, structural, and calcium-binding proteins in the normal adult mouse cerebellum, serving as a critical baseline for future investigations into A-T pathology. Differential expression patterns of protein markers, including Notch1, Phospho-CREB and Akt, neurotrophins, and their receptors, as well as calcium-binding and structural proteins, were evaluated using indirect immunofluorescence and confocal laser scanning microscopy. The cerebellar cortex layers exhibited distinct immunoreactivity patterns. Notch 1 was localized in the internal granular layer and in Bergmann glial fibers, but was unexpectedly absent from Purkinje cells. Conversely, Phospho-CREB and neurotrophins (BDNF, NT-3) were highly expressed in Purkinje cells and the granular layer, reflecting their roles in neuronal survival and synaptic plasticity. Calcium-binding proteins showed varied localization. Indeed, calretinin marked both Purkinje and granular layers, whereas calbindin was notably absent from Purkinje cells. Structural proteins such as vimentin and neurofilaments provided a detailed view of cerebellar architecture, highlighting Bergmann glia and axonal integrity. This study provides detailed molecular records of the physiological mouse cerebellum. These findings highlight both expected and divergent expression patterns compared with the existing literature, particularly for Notch1 and calbindin. This comprehensive mapping is essential for identifying the specific molecular dysregulations in ATM-deficient models, thereby facilitating the identification of potential therapeutic targets for Ataxia-Telangiectasia. This study was conducted as part of the PHARMA-HUB (Hub per il riposizionamento di farmaci nelle malattie rare del sistema nervoso in età pediatrica), funded by the Piano di Sviluppo e Coesione del Ministero della Salute 2014-2020 - Piano operativo salute - Traiettoria 4 "Biotecnologia, bioinformatica e sviluppo farmaceutico" (CUP J43C22000500006; identification code T4-AN-04).