Toward Understanding Cranial Sutures in Zebrafish and Chicken

Abstract

Cranial sutures are the fibrous joints between the intramembranous bones of the skull roof that enable the skull to grow in size during the development and growth of the brain. Although the skulls of vertebrate model organisms are broadly similar, mammalian models have been consistently utilized for calvariae-related studies. Zebrafish are an emerging model organism and the chicken embryo is an established model organism in developmental biology. By comparing suture development of these organisms we can gain insight into the universality of how sutures form in vertebrates. A growth series was collected for each species and stained to visualize suture formation. Using morphometric analysis, I statistically analyzed the changes in shape of the sutures over growth. In both organisms, the interfrontal suture forms first. In zebrafish, this is followed by formation of the coronal suture and then the sagittal suture. In the chicken model, suture formation occurs late and only the anterior portion of the interfrontal suture has formed by hatching. The manner in which zebrafish sutures form is more similar to that of humans than is that of chicken. I also investigated the distribution of the protein ephrin-B2a in the zebrafish skull, and compared it to that previously found in the cranial sutures of mice. No efnb2a was detected in the zebrafish skull roof. By comparing suture formation of these organisms and learning more about the distribution of ephrin-B2a, I have gained insight into how these organisms can be utilized to understand craniosynostosis and other disorders that affect the skull roof.