MEMO1 is required for ameloblast maturation and functional enamel formation
Coordinated mineralization of soft tissue is central to organismal form and function, while dysregulated mineralization underlies several human pathologies. Oral epithelial derived ameloblasts are polarized, secretory cells responsible for generating enamel, the most mineralized substance in the human body. Defects in ameloblast development result in enamel anomalies, including amelogenesis imperfecta. Identifying proteins critical in ameloblast development can provide insight into specific pathologies associated with enamel related disorders or more broadly, mechanisms of mineralization. Previous studies identified a role for MEMO1 in bone mineralization; however, whether MEMO1 functions in the generation of additional mineralized structures remains unknown. Here, we identify a critical role for MEMO1 in enamel mineralization. First, we identified that Memo1 is expressed in ameloblasts and that conditional deletion of Memo1 from ameloblasts results in enamel defects, characterized by a decline in mineral density and tooth integrity. Molecular profiling of ameloblasts and their progenitors in Memo1 oral epithelial mutants revealed a disruption to cytoskeletal associated genes and a reduction in late stage ameloblast markers, relative to controls. Histology revealed that the molecular defects correlated with a disruption of the apical Tome's process and the basolateral interacting, papillary layer, in Memo1 mutant ameloblasts. Finally, deletion of Memo1 from an oral epithelial ameloblast cell line, followed by cellular and molecular analyses, revealed altered cytoskeletal networks, relative to control cells. Collectively, our findings integrate MEMO1 into an emerging network of molecules important for ameloblast development and provide both in vivo and in vitro systems to further interrogate the relationship of cytoskeletal and amelogenesis-related defects. Overall design: single cell RNA-sequencing of Memo1 mutant mouse ameloblast lineages and control tissue