A novel model for exploring craniofacial birth defects

Objectives: Previous research has shown that the oxidative stress-inducing compound auranofin (AFN) may cause craniofacial cartilage defects in zebrafish embryos. The aim of this study is to determine how genetic and environmental causes of craniofacial birth defects affect the growth and survival of cells contributing to the craniofacial skeleton during embryo development. Using a zebrafish model, we want to determine whether factors that enhance cell survival can actually rescue craniofacial defects.
Methods: AFN was applied to zebrafish embryos and the resulting cartilaginous phenotype was characterised at 5 days post-fertilisation (dpf) using light microscopy. To determine whether craniofacial defects were due to cell death, we used terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Photos were taken of embryos at different timepoints and AFN concentrations, to see if there was a difference in the number of cells stained. An antioxidant, RiboCeine (RBC), was added in conjunction with AFN to investigate whether the phenotype produced by applying AFN can be rescued by antioxidants via promoting cell survival. The resulting phenotypes were characterised at 5 dpf using light microscopy.
Results: Application of AFN caused defects in craniofacial cartilage of 5 dpf zebrafish embryos. Higher doses of AFN led to greater numbers of TUNEL-positive cells, therefore the craniofacial defects observed are likely due to cell death. Dying cells probably include those of neural crest origin, since these are the primary source of the craniofacial skeleton. Strikingly, RBC consistently ‘rescued’ the jaw-defect phenotype caused by the the application of AFN.
Conclusions: An antioxidant, RBC, can rescue craniofacial cartilage defects caused by the oxidizing agent AFN in a zebrafish model, and may have translational significance. Indeed, treatment with antioxidants may help to prevent craniofacial defects in children, especially in families where there is an identified genetic or environmental risk.