Spatiotemporal single-cell atlas of suture stem cell dynamics in craniosynostosis.

BACKGROUND: Craniosynostosis is a congenital disorder characterized by premature suture fusion and aberrant skull morphogenesis. The cellular dynamics and regulatory mechanisms of suture mesenchymal stem cells (SuSCs) in this disease remain poorly defined. METHODS: We integrated single-cell RNA sequencing and 2-μm-resolution Visium HD spatial transcriptomics to build a spatiotemporal atlas of coronal suture cells in Fgfr2C342Y/+ mice, a murine model recapitulating human Crouzon syndrome, alongside wild-type controls across three key developmental stages (E14.5, E18.5, and P3). To obtain near single-cell spatial resolution, we created SpatialCell, which combines morphology-based segmentation and machine-learning classification using a reference trained on our single-cell datasets. RESULTS: The atlas reveals stage-specific remodeling of SuSC niches and a shift of SuSC spatial associations toward osteogenic mesenchyme in craniosynostosis. Along the SuSC-to-osteoblast trajectory, pre-osteoblasts were depleted earlier than upstream SuSCs, and SuSCs displayed premature acquisition of osteogenic programs near the suture midline. Temporal Gene Ontology patterns indicated early extracellular-matrix disruption, mid-gestation chondrogenic activation, and postnatal mineralization. Network analysis nominated Foxa3 as a candidate regulator in SuSC subsets; siRNA knockdown of Foxa3 reduced ex vivo mineralization in the craniosynostosis background. Spatial communication analyses implicated signals from suture meningeal fibroblasts and immune cells that converge on SuSC fate. CONCLUSIONS: Our results support a model where craniosynostosis may involve disrupted temporal coordination of developmental programs, not merely accelerated bone formation. The atlas and analytic framework pinpoint when and where SuSC fate diverges, propose Foxa3 as an intervention target, and provide a high-resolution resource for mechanistic and therapeutic exploration.