Craniomaxillofacial morphology in a murine model of ephrinB1 conditional deletion in osteoprogenitor cells.

Objective: EFNB1 mutation causes craniofrontonasal dysplasia (CFND), a congenital syndrome associated with craniomaxillofacial anomalies characterised by coronal craniosynostosis, orbital hypertelorism, and midface dysplasia. The aim of this murine study was to investigate the effect of the EfnB1 conditional gene deletion in osteoprogenitor cells on the craniomaxillofacial skeletal morphology.
Design: The skulls of male and female mice, in which EfnB1 was deleted by Cre (a site-specific DNA recombinase) under the control of the Osterix (Osx) promoter (EfnB1 _OB ^-/- ), were compared to those without EfnB1 deletion (Osx:Cre control) at two ages (4 and 8 weeks; n = 6 per group). The three-dimensional micro-computed tomography reconstructions were prepared to calculate 17 linear measurements in the cranial vault (brain box), midface and mandible. Coronal and sagittal sutures from the 8-week-old mice were also subjected to histological examination.
Results: EfnB1 _OB ^-/- mice displayed significantly larger cranial height, larger interorbital and nasal widths, smaller maxillary width than controls by 8 weeks (p < 0.05), but mandibular size was not significantly different (p > 0.05). Binomial testing showed significantly smaller EfnB1 _OB ^-/- skulls at 4 weeks but larger at 8 weeks (p < 0.05). Histological examination revealed increased bony fusion and fibrous connective tissue deposition at the coronal suture of EfnB1 _OB -/- mice compared with controls.
Conclusions: Craniofacial phenotype of the murine model of EfnB1 deletion in osteoprogenitor cells partially represents the human CFND phenotype, with implications for better understanding mechanisms involved in skeletal morphogenesis and malocclusion.
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