Table 1.
Genetic background-dependent exencephaly in the Pax-2 mutant
| Mice | 129sv (n = 122)
|
C57B6 (n = 184)
|
||
|---|---|---|---|---|
| Normal | Exencephalus | Normal | Exencephalus | |
| wt | 100% | 0% | 100% | 0% |
| −/+ | 100% | 0% | 100% | 0% |
| −/− | 0% | 100% | 70% | 30% |
All of the homozygous mice of the 129sv strain showed exencephaly, but none of the heterozygous or the wild-type ones did so. In the mutants backcrossed into the C57BL/6 strain, the percentage of exencephaly in the homozygous animals decreased to 30%. The offspring of heterozygous crosses was genotyped and analyzed at different stages of development. All the cases of exencephaly were immediately observable as severe morphological alterations. wt, wild type.