The time of palatal fusion in mice: a factor of strain susceptibility to teratogens.

Induction of facial clefts in an animal model is often performed in experimental teratology. The susceptibility to teratogens of different strains of mice is genetically determined and seems to depend on the time of palatal fusion during embryogenesis. In order to elucidate the mode of action of preventive measures, we determined the exact time of palatal fusion in different strains of mice used for experiments in our laboratory. Fusion of the secondary palate is finished in the Halle: NMRI-mice at day 15, 0 h of gestation, in Halle: DBA and in A/WySnJ mice at day 15, 6 h and in the Halle: Jena AB-mice at day 15, 12 h. This sequence is at variance with spontaneous cleft rates and susceptibility to teratogens.