Developmental alterations associated with spontaneous cleft lip and palate in CL/Fr mice.

Cleft lip with or without associated cleft palate [CL(P)], one of the most common human malformations, is believed to be caused by a combination of genetic and environmental factors. To study the morphological manifestations of genetic factors in this interaction, we compared the embryonic development of the CL/Fr mouse strain (with a mean incidence of 36% spontaneous CL(P) in our colony) with that of the C57B1/6J mouse strain (with no CL(P) in our colony). Results from our scanning electron microscopic study demonstrated that, when compared with C57B1/6J embryos, CL/Fr embryos have several developmental differences including: 1) altered facial geometry, 2) depressed ability of the surface epithelium of primary-palate primordia to participate in the fusion process, and 3) variable hypoplasia of the lateral nasal prominences. We suggest that all of these alterations may contribute to the pathogenesis of CL(P) in the CL/Fr mouse strain.