Shiverer∗jimpy double mutant mice. III. Comparison of shi mld∗ jp msd and shi∗ jp phenotypes demonstrates dissimilar interactions of allelic mutations

Abstract

Double mutant mice, which are of the genotype shi mld/shi mld ∗ jp msd/Y and therefore express both the shi mld and jp msd mutations, have a CNS myelin protein composition which resembles shi mld/shi mld alone but not jp msd/Y alone. The double mutant CNS white matter morphology shows much less myelin and major dense line than either shi mld/shi mld or jp msd/Y , but has other features which resemble jp msd/Y but not shi mld/shi mld . In contrast, the parallel double mutant shi/shi∗jp/Y, which expresses the alleles shi and jp rather than shi mld and jp msd , has already been shown to have biochemical and morphological phenotypes which are consistent with each other, both being intermediate between shi/shi and jp/Y and therefore suggesting partial reciprocal intergenic suppression ( Brain Research, 374 (1986) 45–53 and 54–62). To assist in explaining the apparent inconsistencies between the biochemical and morphological phenotypes of the shi mld/shi mld ∗ jp msd/Y double mutant and between interactions of allelic mutations at the shi and jp loci, a hypothesis of multiple primary gene functions at these two loci is proposed.