https://phys.org/news/2018-10-zebrafish-common-craniofacial-birth-defect.html

"Mouse models for this birth defect have already been developed," said Crump, a professor of stem cell biology and regenerative medicine at the Keck School of Medicine of USC. "Our goal was to create a zebrafish model to better understand stem cell dysfunction in this disorder, as we can more easily manipulate and watch how skull development goes awry in this transparent vertebrate that shares many genes in common with us." In the study, first author Camilla Teng and her colleagues generated zebrafish with mutations in two key genes that underpin a common form of craniosynostosis called Saethre-Chotzen syndrome. They found that mutations in these genes—known as TCF12 and TWIST1—can cause craniosynostosis in zebrafish, similar to mice and humans. In all three species, the mutations trigger the premature fusion of an important suture at the crown of the skull—aptly named the coronal suture.

Teng and her colleagues observed these live transgenic zebrafish as they developed. Zebrafish lay and fertilize their eggs in the water outside of their bodies, and their embryos are completely transparent. Therefore, the scientists were able to observe details of early embryonic development that are obscured within the wombs of mammalian species, such as lab mice.