ESPE Abstracts

Expansion of the skull vault to accommodate the growing brain is driven primarily by growth at cranial sutures. These are fibrous joints between the flat bones of the skull that translate growth pressure from the brain into a balanced proliferation and differentiation of cells of the osteoblast lineage. This process is sensitive to environmental and genetic insults and premature fusion of one or more sutures, termed craniosynostosis is a common (~1 in 2000), and serious craniofacial malformation. In about a quarter of all cases a monogenic cause can be identified with mutations in over 100 genes associated with craniosynostosis. Analysis of mouse models for some of these genes highlights the role of abnormalities in both developmental patterning and in proliferation-differentiation balance in craniosynostosis. Better delineation of these mechanisms requires a clearer understanding of the cell populations that make up a cranial suture. In recent work we generated single-cell transcriptomes from murine coronal sutures and performed extensive expression validation. We found distinct pre-osteoblast signatures between the bone fronts and periosteum, a ligament-like population above the suture that persists into adulthood, and a chondrogenic-like population in the dura mater underlying the suture. Lineage tracing revealed an embryonic Six2+ osteoprogenitor population that contributes to the postnatal suture mesenchyme, with these progenitors being preferentially affected in a Twist1+/-; Tcf12+/- mouse model of Saethre-Chotzen Syndrome.