Palatal shelf movement during palatogenesis: a fate map of the fetal mouse palate cultured in vitro.

Day-13 fetal mouse palates (plug day=day 0) were labeled with carbon particles at various sites of palatal shelves and cultivated in a chemically defined medium for up to 48 h. During the culture period, the bilateral palatal shelves came in contact and fused with each other, which simulated in vivo palatogenesis. The carbon study revealed that at the midpalatal region, the medial edge of the palatal shelf elevated to the horizontal plane, elongated toward the midline, and made contact with the medial edge of the opposing shelf. On the other hand, near the anterior and posterior ends of the shelf, some new tissue was formed at the medial edge of the shelf by remodeling and this newly formed tissue took part in palatal fusion. The results of the present study indicate that during mouse palatogenesis, the anterior and posterior regions of the palatal shelf behave differently from the midpalatal region. It seems that in the fetal mouse palate, the midpalate closes mainly by means of rotation and medial elongation of the shelf, whereas the anterior and posterior parts of the palate close mainly by tissue remodeling of the medial edge and partly by medial elongation of the shelf.