MyosinX is Required For Craniofacial Development in Danio Rerio

Craniofacial development is the process of laying early cartilage and bone patterns in the anterior region of the embryo, which ultimately results in shaping the structure of the face and head of an organism. Craniofacial abnormalities in humans, such as cleft lip and palate, are among the most common of all birth defects. Therefore, investigating the molecular mechanisms involved in craniofacial development will help us understand both evolutionary processes and genetic diseases. Craniofacial cartilage and bone structures are almost entirely derived from neural crest cells. Neural crest are a pluripotent migratory stream of cells that originate from the early developing brain and settle in final positions that give rise to the future skull and face. Several motor proteins are implicated in the migration of these neural crest cells. We have identified and isolated zebrafish myosinX mutants with defective craniofacial development. Currently, we are characterizing the role of myosinX in craniofacial development using various staining techniques. Alcian blue staining was used to identify specific defects within the cartilage, specifically ceratobranchial arches 3-5 are distorted or completely missing in myosinX deficient embryos. Using alizarin red staining techniques, pharyngeal tooth development was also examined. Tooth development occurs on the fifth ceratobranchial arch in a three crown clustered manner. However, in myosinX deficient zebrafish, pharyngeal crown protrusion was significantly hindered, showing only one developing crown within the tooth in most morphant embryos. This study used immunohistochemical staining as well as RNA in situ hybridization techniques to identify the specification and position of migrating neural crest cells to establish a link between myosinX and neural crest cell migration during early development. In myoX morphant and mutant individuals, craniofacial structures are significantly deformed compared to wildtype and control individuals. In addition, cranial neural crest cell migration is inhibited in myoX morphant and mutant individuals