Cytoplasmatic polyadenylation of mRNA by TENT5A is critical for enamel mineralization

Tooth enamel formation, or amelogenesis, is a complex biomineralization process regulated by ameloblasts cells. These cells secrete enamel matrix proteins (EMPs), including Amelogenin (AMELX) and Ameloblastin (AMBN), which are essential for hydroxyapatite crystal deposition during enamel mineralization. Precise regulation of this process ensures the mechanical and chemical strength of dental enamel. Using Tent5a knock-out (KO) mouse, we demonstrated that TENT5A, a non-canonical poly(A) polymerase is crucial for the stability, translation, and secretion of EMP mRNAs, particularly AMELX, during amelogenesis. TENT5A-deficient mice exhibited Amelogenesis imperfecta, characterized by enamel hypomineralization, reduced thickness, and disrupted ultrastructure, as revealed by micro-computed tomography. Through nanopore direct mRNA sequencing, we identified that TENT5A polyadenylates Amelx and other mRNAs encoding secreted proteins, enhancing their stability and translation in the endoplasmic reticulum. Moreover, loss of TENT5A altered AMELX secretion and extracellular self-assembly, impairing matrix organization and hydroxyapatite deposition. This study highlights the role of TENT5A in post-transcriptional regulation during enamel formation, demonstrating its importance in enamel homeostasis.