Strain differences in heat-induced neural tube defects in mice.

Neural tube defects are common congenital anomalies affecting approximately 0.1% of liveborn infants. It is widely accepted that these disorders are of a multifactorial origin, having both a genetic and an environmental component to their development. In a study designed to elucidate the genetic factors involved in a mouse model of hyperthermia-induced neural tube defects, it is apparent that a hierarchy of susceptibility exists among various inbred mouse strains. Female SWV mice were extremely sensitive to a 10-minute hyperthermic treatment on day 8.5 of gestation, with 44.3% of their offspring having exencephaly. The other strains used in these studies (LM/Bc, SWR/J, C57BL/6J, and DBA/2J) all had less than 14% affected offspring. In experimental situations where the environment is held constant and the only difference between the strains is their genotype, it is assumed that the difference in response to a teratogen is genetically mediated. To test the hypothesis that several genes are involved, reciprocal crosses were made between strains of high, moderate, and low sensitivity. When this was done, the high sensitivity of the SWV strain was lost in the F1 hybrid, implying not only that multiple genes are involved, but that it is the embryo's genotype and not the maternal genotype that is the major factor in determining susceptibility to heat-induced neural tube defects.