AUTHOR=Raju Resmi , Piña Jeremie Oliver , Roth Daniela M. , Chattaraj Parna , Kidwai Fahad K. , Faucz Fabio R. , Iben James , Fridell Gus , Dale Ryan K. , D’Souza Rena N. 

TITLE=Profiles of Wnt pathway gene expression during tooth morphogenesis

JOURNAL=Frontiers in Physiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1316635

DOI=10.3389/fphys.2023.1316635

ISSN=1664-042X

ABSTRACT=<p>Mouse and human genetic studies indicate key roles of the <italic>Wnt10a</italic> ligand in odontogenesis. Previous studies have identified effectors and regulators of the Wnt signaling pathway actively expressed during key stages of tooth morphogenesis. However, limitations in multiplexing and spatial resolution hindered a more comprehensive analysis of these signaling molecules. Here, profiling of transcriptomes using fluorescent multiplex <italic>in situ</italic> hybridization and single-cell RNA-sequencing (scRNA-seq) provide robust insight into the synchronized expression patterns of <italic>Wnt10a</italic>, <italic>Dkk1</italic>, and <italic>Sost</italic> simultaneously during tooth development. First, we identified <italic>Wnt10a</italic> transcripts restricted to the epithelium at the stage of tooth bud morphogenesis, contrasting that of <italic>Sost</italic> and <italic>Dkk1</italic> localization to the dental mesenchyme. By embryonic day 15.5 (E15.5), a marked shift of <italic>Wnt10a</italic> expression from dental epithelium to mesenchyme was noted, while <italic>Sost</italic> and <italic>Dkk1</italic> expression remained enriched in the mesenchyme. By postnatal day 0 (P0), co-localization patterns of <italic>Wnt10a</italic>, <italic>Dkk1</italic>, and <italic>Sost</italic> were observed in both terminally differentiating and secreting odontoblasts of molars and incisors. Interestingly, <italic>Wnt10a</italic> exhibited robust expression in fully differentiated ameloblasts at the developing cusp tip of both molars and incisors, an observation not previously noted in prior studies. At P7 and 14, after the mineralization of dentin and enamel, <italic>Wnt10a</italic> expression was limited to odontoblasts. Meanwhile, Wnt modulators showed reduced or absent signals in molars. In contrast, strong signals persisted in ameloblasts (for <italic>Wnt10a</italic>) and odontoblasts (for <italic>Wnt10a</italic>, <italic>Sost</italic>, and <italic>Dkk1</italic>) towards the proximal end of incisors, near the cervical loop. Our scRNA-seq analysis used CellChat to further contextualize Wnt pathway-mediated communication between cells by examining ligand-receptor interactions among different clusters. The co-localization pattern of <italic>Wnt10a</italic>, <italic>Dkk1</italic>, and <italic>Sost</italic> in both terminally differentiating and secreting odontoblasts of molars and incisors potentially signifies the crucial ligand-modulator interaction along the gradient of cytodifferentiation starting from each cusp tip towards the apical region. These data provide cell type-specific insight into the role of Wnt ligands and mediators during epithelial-mesenchymal interactions in odontogenesis.</p>