Loss of GlialCAM cytoplasmic signaling drives cerebellar white matter vacuolation through glial reprogramming and disrupted cell-cell communication

Glial cell adhesion molecule (GlialCAM) is a transmembrane protein enriched in astrocytes and oligodendrocytes and is required for white matter homeostasis. While prior studies have focused on extracellular cell-cell adhesion functions for GlialCAM, the contribution of its cytoplasmic signaling domain remains unclear. Here, we generated a mouse model, termed GCAMΔCT, in which the cytoplasmic tail of GlialCAM is selectively deleted in the brain while preserving its extracellular and transmembrane domains. Mutant mice develop progressive vacuolation of cerebellar white matter, accompanied by deficits in motor coordination and recognition memory. Histological and ultrastructural analyses revealed widespread disruption of myelinated tracts. Single-cell RNA sequencing of cortical and cerebellar regions identified broad transcriptional reprogramming in glial cells, characterized by upregulation of inflammatory pathways and extracellular matrix (ECM) remodeling programs. Spatial transcriptomic analysis localized these transcriptional changes to vacuolated white matter regions, where astrocytes and oligodendrocytes exhibited increased expression of ECM components and reactive glial markers. Integration of single-cell and spatial datasets further revealed a marked reduction in glial cell-cell communication networks, including loss of trophic and neurotransmitter-associated signaling pathways, together with increased signaling associated with ECM remodeling and stress responses. Collectively, these findings indicate that the GlialCAM cytoplasmic domain is necessary for normal white matter structure and function and suggest that this occurs at least in part through alterations in glial transcriptional programs and cell-cell signaling networks.