Oral Presentation ANZBMS-MEPSA-ANZORS 2022

Mice lacking ephrinB1 in the osteogenic lineage display craniomaxillofacial abnormalities (#41)

Samuel Bereza 1 , Robin Yong 1 , Stan Gronthos 2 3 , Sarbin Ranjitkar 1 , Peter Anderson 1 2 4 , Agnieszka Arthur 2 5
  1. Adelaide Dental School, The University of Adelaide, Adelaide, SA, Australia
  2. South Australian Health and Medical Research Institute, Adelaide, SA, Australia
  3. Mesenchymal Stem Cell Laboratory, School of Biomedicine, The University of Adelaide, Adelaide, SA, Australia
  4. Australian Craniofacial Unit, Women’s and Children’s Hospital, Adelaide, SA
  5. Musculoskeletal Cellular Communication laboratory, School of Biomedicine, The University of Adelaide, Adelaide, SA, Australia

Mutations in human ephrinB1 (EFNB1) manifest in craniofrontonasal dysplasia (CFND), several features include craniomaxillofacial abnormalities such as midface dysplasia, orbital hypertelorism and coronal craniosynostosis. The only current treatment for children with CFND is repeated surgical intervention. There are limited tools available to investigate ephrinB1 induced CFND. The present study aimed to determine whether loss of EfnB1 in the murine osteogenic linage, under the regulation of the Osterix (Osx) promoter caused CFND associated craniomaxillofacial abnormalities. Osterix is a transcription factor essential for osteogenesis and is expressed within the cranium from embryonic day (E)12.5-13.5.

Female and male skulls from 4-week and 8-week-old mice with a Cre mediated deletion of EfnB1 in osteoprogenitors, under the control of the Osx promoter (EfnB1OB-/-) were compared to control (Osx:Cre) mice (n = 6 / group). These samples underwent three-dimensional micro-computed tomography (µCT), reconstruction and morphometric analysis. Coronal and sagittal sutures were subsequently processed and stained for haematoxylin and eosin.

Morphometric analysis demonstrated that EfnB1OB-/- skulls from female and male mice collectively were smaller at 4 weeks-of-age and bigger at 8 weeks-of-age compared to the Osx:Cre controls (MANOVA, p < 0.05). More specifically, 8-week-old EfnB1OB-/- mice exhibited a significant increase in cranial height, interorbital (between the eyes) width and nasal width, and a reduction in maxillary (upper jaw) width when compared to the Osx:Cre controls (p < 0.05). There were no significant changes in mandibular (lower jaw) dimensions between Osx:Cre controls and EfnB1OB-/- mice (p > 0.05). However, histological assessment of 8-week-old coronal sutures morphology identified early signs of suture fusion and changes in connective tissue in EfnB1OB-/- mice compared to Osx:Cre mice.

Collectively, this data suggests that EfnB1OB-/- mice display phenotypic craniofacial characteristics partially consistent with the human CFND phenotype. This model could be utilised to investigate the cellular and molecular mechanisms involved in cranial morphogenesis.