Electrophoretic Variation and Sex Dimorphism of the Major Urinary Protein Complex in Inbred Mice: A New Genetic Marker

Abstract

The urinary proteins of both sexes from 19 inbred strains of mice and 2 hybrids were examined by agar-gel electrophoresis and Immunoelectrophoresis with rabbit antisera. The mice excreted several different proteins, but amounts of the major urinary protein (MUP) greatly exceeded all others. At pH 5.5, three different electrophoretic components of MUP could be distinguished. In any inbred strain only 2 of the components were evident, and they varied in relative amounts. On this basis several MUP phenotypes were designated. Although 2 male and 4 female phenotypes were seen, only 4 male-female combinations were observed in the 19 strains examined. When 2 parental strains of similar phenotype were mated, the MUP components of the respective F₁ hybrids were like those of the parent of the same sex. When 2 unlike parental strains were mated, the F₁ hybrids of both sexes had a different phenotype from either parent, all 3 components being present. Ovariectomized, testosterone-treated females exhibited the MUP phenotype characteristic of the males of the strain, but the pattern returned to the female phenotype when testosterone injections were discontinued. Castrated males had the pattern characteristic of females. The MUP complex thus provides a suitable system for the study of genetic and hormonal influences on protein synthesis.