Fig 1: Reduced osteoprogenitor pool at the mutant coronal suture.(A, B) Sections of forming coronal and sagittal sutures of 10 mm fish and fully formed sutures of adult fish were assessed for gli1, grem1a, and prrx1a mRNA expression (white) by RNAscope in situ hybridization. Orange dotted lines indicate bones, and the boxed regions of the coronal suture regions are magnified below. For adult sutures, yellow arrowheads show expression in the suture mesenchyme, yellow arrows show expression of prrx1a in the periosteum, and grew arrows show lack of expression of gli1 and grem1a in the periosteum. Scale bar at 10 mm stage, 20 µm; scale bar at adult stage, 50 µm. (C, D) Sections of E14.5 coronal sutures and E16.5 forming sagittal sutures of mice stained for Gli1/Grem1 (magenta) and Sp7 protein (green). Yellow arrowheads indicate progenitor regions in forming coronal sutures. Boxed regions of parietal bone fronts in the forming sagittal sutures are magnified in lower panels. Nuclei are stained blue by DAPI in all images. Scale bars, 100 µm.