Proliferation and Apoptosis in Cleft Palate of Wnt5a Knockout Mice

Objective: To investigate the functional role of Wnt5a in secondary palate development by detecting cell proliferation and apoptosis in Wnt5a knockout mice. Methods: Wnt5a knockout mice were kindly provided by Dr. Andrew McMahon (Harvard University). In E13.5, E14.5, E15.5 and E16.5 Wnt5a knockout mice and control, serial frontal sections of heads were made to determine the morphological changes of secondary palate. Futhermore, proliferation assay was performed with bromodeoxyuridine (BrdU) staining, and apoptosis cells were detected by terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL). Results: Wnt5a knockout mice died soon after birth with the truncation of the proximal comonents and entire absence of distal-most limb structures, as well as distinct abnormalities in trachea and distal respiratory airways. Histologically, Wnt5a knockout mice showed delayed proximal-distal outgrowth of secondary palate at E14.5, failed fusion of secondary palate at E15.5 and completely formation of cleft palate at E16.5. The proliferation ratio was analyzed by performing BrdU staining in Wnt5a knockout mice at E14.5, no difference showed between the mesenchymal components of palate, as well as tongue and tooth germ. But the medial edge epithelium (MEE) of E14.5 Wnt5a knockout mice palate showed negative staining of BrdU. In TUNEL analysis of Wnt5a knockout and control mice at E15.5, the apoptosis positive cells were detected abnormally localization in oral epithelium of Wnt5a knockout mice, in comparison with normally in MEE of control mice; and rather large amounts of TUNEL positive cells were also detected in Wnt5a knockout tongue. Conclusion: Our data suggested Wnt5a gene may play important roles in secondary palate development by regulating both cell proliferation and apoptosis.