Distribution of p21ras during primary palate formation of non-cleft and cleft strains of mice.

Cleft lip, with or without cleft palate, is one of the most common defects in craniofacial formation. The primary palatogenesis of mice is similar to that of humans and spontaneous cleft lip is associated with genotype in both mice and humans. To investigate the temporal and spatial expression of ras genes in cleft (A/WySn) and non-cleft strains of mice (BALB/cBy), a broad spectrum ras antibody was used. Positive staining was found in ectodermal, mesenchymal, and neuroepithelial cells of facial prominences before the primary palate formation stage (10 d 20 hr) in both strains. During the primary palate formation stage (11 d 20 hr), positive staining was found in the ectodermal and mesenchymal cells of the facial prominences of the non-cleft strain but not in those of the cleft strain. These results suggest ras genes may play a role in the primary palatogenesis of mice. Cleft lip could be associated with the deficiency of ras gene expression during primary palate formation of mice.