Figure 1.

(A) Clinical photographs and CT head scans of individuals 7081 aged 7 months (left) and 4531 aged 2.5 years (right), probands of families 1 and 7, respectively. Note the fused sagittal sutures (filled arrowheads), and in 7081 lambdoid sutures (unfilled arrowheads). The coronal sutures are patent (arrows). (B) Pedigrees of families harbouring missense (blue lettering) or nonsense (red lettering) variants in SIX1; individuals affected with CRS shown with black fill (left side of the pedigree symbol) and individuals with BOS features shown with black or grey fill according to severity (right side of the pedigree symbol; mild: preauricular pit or late-onset HL; severe: branchial cyst/fistula or congenital HL). Genotypes are indicated for all available samples. (C) SIX1 variants in congenital disease. (Left) Domain structure of the human SIX1 protein showing the locations of the six domain (SD) and homeodomain (HD). Pathogenic variants, colour-coded according to the key at far right, are shown (above the protein cartoon) for the seven CRS-associated variants identified in this work and (below the cartoon) for previously identified variants in BOS/BOR/HL syndromes. (Right) The chart represents the number of different variants of each pathogenic class identified in CRS or in BOS/BOR/HL. (D–E) SIX1 protein expression revealed by X-gal staining in frontal sections (10 µm thick) of E18.5 Six1^nLacZ/+ mouse heads. (D) Representation of the mouse skull from above to illustrate the plane of section (coronal) in the histological sections shown (p, parietal bone; f, frontal bone). (E) Arrows indicate the superior margins of the parietal bones, and the dotted box (enlarged in a nearby section in (F) shows the sagittal suture. Blue nuclei (X-gal positive) indicate SIX1 expression. Scale bars: 500 µm (E) and 150 µm (F). BOR, branchio-oto-renal; BOS, branchio-otic syndrome; CRS, craniosynostosis; HL, hearing loss.