Differential in vitro response to epidermal growth factor by prenatal murine cranial-base chondrocytes.

The retrognathic Brachyrrhine (Br) heterozygote mouse mutant has a very localized morphological deficiency in the sphenoethmoidal region of the anterior cranial base. The purpose of this study was to test the hypothesis that a primary growth defect occurs in that region of Br mice. Primary cell cultures were derived from presumptive nasal septal and sphenoethmoidal regions of Br and wild-type littermates. Cultures were stimulated with 1.0 ng/ml epidermal growth factor (EGF), and [3H]thymidine and [35S] incorporation was measured. Growth of the nasal septal chondrocytes did not differ significantly between groups. In the cultures derived from the sphenoethmoidal region [35S] incorporation was greater, but not significantly so, in the normal group. However, EGF did significantly stimulate proliferation of the sphenoethmoidal chondrocytes in wild-type cultures above that measured in Br cultures. Therefore, the Br genetic aberration is associated with a primary growth defect in the sphenoethmoidal region of the cranial base. These results suggest that growth of the anterior cranial base occurs differentially and that the defect in Br mice results in reduced sphenoidal but not nasal septal growth.