Expression Analysis of Jagged2 Gene in Craniofacial Development

The Notch signaling pathway has been shown to be implicated during craniofacial development. Activation of Notch signaling pathway requires binding by its ligands. Jagged 2 is one of the Notch ligands. Deletion of Jagged2 gene in mice has resulted in cleft palate phenotype. Objective: To analyze the expression pattern of Jagged2 in craniofacial development especially during secondary palate formation. Methods: Whole-mount in situ hybridization was performed on wild-type mouse embryos from E9.5 to E14.5 using the Jagged2 probe. Immunohistochemistry was done on tissue sections of E12.5 to E15.5 using Jagged2 antibody. Skeletal and histological analyses were performed on wild-type and Jagged2 mutant littermates to asses the differences in secondary palate formation. Results: Jagged2 was expressed in the epithelial cell layer of the branchial arches and the area surrounding the nasal pits of E9.5, E10.5 and E11.5 embryos. During palate development, Jagged2 transcripts were expressed throughout the surface of the developing palatal shelves of E12.5 and E13.5 but down-regulated in E14.5. Jagged2 protein expression corresponds to these domains; interestingly, it appears to be expressed in the area of epithelial-mesenchymal interactions such as in the tooth germs and the boundary between the maxilla and the mandible formation. In addition to abnormal fusion in the oral cavity between the mandibular and maxillary shelves, histology and skeletal analysis also confirmed the glossopalatal fusion observed in Jagged2 null mice leads to cleft palate. Conclusion: These expression analyses demonstrate the importance of Jagged2 during craniofacial development and palatogenesis.