Single-cell analysis identifies a key role for Hhip in murine coronal suture development

Craniofacial development depends on proper formation and maintenance of sutures between adjacent bones of the skull. In sutures, bone growth occurs at the edge of each bone, and suture mesenchyme maintains the separation between them. We performed single-cell RNA-seq analyses of the embryonic, murine coronal suture. Analyzing replicate libraries at E16.5 and E18.5, we identified 14 cell populations. Seven populations at E16.5 and nine at E18.5 comprised the suture mesenchyme, osteogenic cells, and associated populations. Through an integrated analysis with bulk RNA-seq data, we found a distinct coronal suture mesenchyme population compared to other neurocranial sutures, marked by expression of Hhip, an inhibitor of hedgehog signaling. We found that at E18.5, Hhip-/- coronal osteogenic fronts are closely apposed and suture mesenchyme is depleted, demonstrating that Hhip is required for coronal suture development. Our transcriptomic approach provides a rich resource for insight into normal and abnormal development.