INSTRUCTION BY RETINOIC ACID OF INCISOR MORPHOLOGY IN THE MOUSE EMBRYONIC MANDIBLE

Endogenous retinoids are present in the embryonic mouse mandible and r each a peak in concentration at the time of the formation of the denta l lamina. All-trans retinoic acid is present in a 10-fold higher conce ntration in the future incisor region of the mouse embryonic mandible at day 11.5. It was found here that exogenous all-trans retinoic acid has pleiotropic effects on the pattern of odontogenesis when applied b efore the formation of the dental lamina. These effects include a chan ge in the pattern of the dental lamina, supernumerary buds and incisor s in the diastema region, and replacement of molars with incisors in t he molar region. Thus retinoic acid appears to instruct incisor morpho logy in the mouse embryonic mandible.