The timing of CNC migration is critical for dental patterning

Objectives: Dental patterning requires teeth with different shape positioned in the specific region of the first branchial arch. The present study was designed to explore the relationship between the time point of neural crest cell (CNC) migration and dental patterning.Methods: Three groups of explantation were carried out as follows: 1)The first arches were dissected out from embryos with different somite stage (E8.0-E11.5). 2)Hemisectioned the first arches were taken from E9.5 and E9.75 embryos. 3)The first arches with dorsal tissues were taken from E9.5 embryos. The above tissues were grafted for culture under kidney capsules in adult mice for 4 weeks respectively. The shape and size of tooth formation were analyzed.Result: The grafts of the first arch from E8.5 (8-10 somite) or earlier yielded membranous bone and cysts but no teeth. The grafts of the first arch from E9.0 (14-15 somite) or E 9.5 (21-22 somite) produced one multicuspid molar. The grafts of the first arch from E9.75 (24-25 somite) to E11.5(44 somite) could form one molar and one incisor. The cusp number and size of the molars were increased from E9.0 to E11.5 grafts. However, the grafts of mesiodistal half-arches of E9.5 and E9.75 only formed bone and cysts. The grafts of the first arch with its dorsal tissues containing migrating CNC from the E9.5 embryos yielded one molar and one incisor.Conclusion: These results indicate that the timing of CNC migration is critical for dental patterning. And the CNC migrated to the first branchial arch should accumulate to a certain number to form molar or incisor.

Key Words: Tooth germ; Neural crest cell; Dental patterning

This research was supported by the grants from the National Natural Science Foundation of China (30700947) and Specialized Research Fund for the Doctoral Program of Higher Education (20060486038).