Survival rate of mice heterozygous for the dominant hemimelia mutation depends on the genetic background

A semidominant mutation, dominant hemimelia ( Dh ), causes hindlimb malformations and congenital absence of the spleen. 1,2 Currently, the molecular nature of the Dh mutation remains unknown. Dh is maintained in the inbred mouse strain DH/Sgn by mating male asplenic DH-Dh / + mice with female eusplenic DH-+ / + mice. The Dh / + genotype is identified by the presence of hindlimb malformations and the absence of the spleen. When DH-Chr Y AKR - Dh / + (DH-Dh / + mice carrying the Y chromosome from the AKR/J strain) males were backcrossed to C57BL/6J females for two generations, many N 2 - Dh / + mice of both sexes died during weaning. 3 N 2 - Dh / + males were further backcrossed to C57BL/6J females, but Dh / + males of backcross generations further than N 5 were not obtained. Thus, Dh could not be maintained in a C57BL/6J background. This study further addressed this peculiar phenomenon. Inbred mouse strains C57BL/6J, BALB/cA, and C3H/HeJ were purchased from Clea Japan Inc. (Tokyo, Japan). Experiments were approved by the Institutional Animal Care and Use Committee of the National Institute of Agrobiological Sciences (authorization nos. H28-009 and H30-001).