Paternal inheritance of egg traits in mice: a case of genomic imprinting

Abstract

Summary: Eggs from reciprocal hybrids between the C57BL/6By and BALB/cBy strains were tested for their susceptibility to attack by hyaluronidase and pronase. There were significant reciprocal differences between the F₁females in the responses of their unfertilized eggs to both enzymes. The F₁hybrids from BALB mothers showed the increased susceptibility characteristic of C57BL whilst the F₁hybrids with C57BL mothers were more resistant to both enzymes, like BALB mice. Eggs from the four kinds of reciprocal F₂hybrid females also showed patroclinous patterns of susceptibility. A patroclinous difference was found between reciprocal crosses of the CXBD and CXBE recombinant inbred strains but not in crosses between recombinant inbred strains with similar phenotypes. Cross fostering did not alter the phenotypes of the C57BL and BALB females or those of their reciprocal F₁hybrids. The findings are interpreted in terms of differential genomic imprinting of paternally inherited information. The possible general usefulness of patroclinous differences between reciprocal F₁females in revealing differences in imprinting is noted.