Cell proliferation in the cranial base of A/J mice with 6‐AN‐induced cleft palate

Abstract

Abstract Midsagittal sections of the heads of day 14.5–15.0 control A/J mouse fetuses revealed three areas of rapidly growing cartilage in the cranial base:mesethmoid, presphenoid, and craniopharyngeal. There was a curvature in the presphenoid, which straightened by the time of palatine shelf movement In fetuses of females treated with 6‐aminonicotinamide (6‐AN) on gestation day 13 the presphenoid had not straightened by day 15.5 and these fetuses all had cleft palate. In nontreated mice with spontaneous cleft lip and palate the presphenoid straightening was not impaired. Autoradiographs of [ 3 H] thymidine uptake in the cranial base of experimental fetuses revealed selective impairment of cell proliferation in the presphenoid as judged by a significant decrease in labeled nuclei. It is proposed that straightening of the presphenoid is necessary for palatine shelf movement and normal palate closure.