Effect of the uterine environment on the frequency of spontaneous cleft lip in CL/FR mice.

TLDR: The demonstration of a uterine effect on cleft lip susceptibility suggests that it might be possible to modify the environment in the direction of increased resistance.

Abstract: It was previously shown (Davidson et al., '69) that the A/J female mouse predisposes her offspring to congenital cleft lip, either by providing a uterine environment or cytoplasmic factors that increase susceptibility, or by not providing a cytoplasmically transmitted factor, present in the C57BL/6J strain, that decreases susceptibility to cleft lip. In the present experiment males of the CL/Fr strain, which has a relatively high frequency of cleft lip, were crossed to females of the C57BL/6J strain, and the F1 offspring were backcrossed to CL/Fr animals. Three second backcrosses were made such that embryos of comparable genotype developed in CL/Fr mothers or in hybrid mothers with or without the postulated cytoplasmic factors. The results showed that the maternal effect on cleft lip susceptibility was present in the CL/Fr strain, and was not mediated through the cytoplasm. Maternal age, parity, litter size, and sex and pigmentation of the offspring showed no consistent associations with frequency of cleft lip. The demonstration of a uterine effect on cleft lip susceptibility suggests that it might be possible to modify the environment in the direction of increased resistance.