Tcp-1 gene is not responsible for the maternal lethality effect of Thp mutation in mice.

Embryos receiving either the Thp or the twLub2 mutation from their mother die during gestation. In contrast, heterozygous embryos receiving the mutant chromosome from the father are completely viable. In both Thp and twLub2 mutants, one chromosome 17 carries a deletion, which suggests the existence of a discrete maternal lethality effect locus (Tme). In the region whose deletion is responsible for the Thp or twLub2 mutation, a single gene has been cloned so far, the Tcp-1 gene. In the present study, we examined the expression of Tcp-1 gene in mutant embryos carrying either a maternal or a paternal Thp chromosome to test whether this gene could be involved in the Tme effect. We found that the levels of Tcp-1-specific transcripts were similar in both mutant embryos from reciprocal crosses and corresponded to half the levels found in the normal littermates. In addition, the paternal and maternal Tcp-1 alleles had identical methylation patterns. These results indicate that Tcp-1 is not responsible for the maternal lethality effect, and therefore is not located at the Tme locus.