[Experimental study on cleft lip of CL/Fr mouse using whole embryo culture system].

The incidence of cleft lip in CL/Fr mouse is 18-2500. The purpose of this study is to clarify the cause of cleft lip in CL/Fr mouse using whole embryo culture system which is a useful technique in studying the development of mammalian embryos in vitro. We examined the incidence of cleft lip in CL/Fr and F, mouse embryo (male CL/Fr x female C57BL/6) in vitro. The embryos were explanted on day 10 of gestation (plug day=0) and were cultured during the period of primary palate formation for 40-48 hours. The non-CL (P) producing strain C57BL/6 embryos were used as control. The cleft lip was observed in 84. 4% of the cultured CL/Fr embryos, while C57BL/6 and F1 embryos did not show any cleft lip in utero and in vitro. The incidence of cleft lip in CL/Fr mice showed variations among litters in vtero. However, in the cultured mouse embryos, there was a little variation in the incidence of cleft lip. These results might suggest that all embryos of CL/Fr mice have a genetic predisposition to cleft lip and that the gene (s) related to cleft lip in CL/Fr mouse is (are) recessive against the allele of C57BL/6 strain.