Environmental influences on the preferences of wild female house mice for males of differing t-complex genotypes

Twenty-five percent of wild house mice are heterozygous (+/t) for a deleterious, recessive mutation at the t complex. In previous studies we have demonstrated that wild female house mice can discriminate +/+ from +/t males and show strong preferences for the odors of males who do not carry t mutations. In the present study we examine the extent to which preferences of +/+ female mice are influenced by the genotype of their parents and or littermates. Our data indicate that when +/+ females are reared by two +/+ parents, they exhibit strong preferences for the odors of +/+ males. In contrast, when a +/+ female is reared by one +/+ and one +/t parent she shows no preference for males of either genotype. A second experiment using mice carrying recombinant chromosomes indicates that the genes responsible for the parental (or family) odor cue are not the deleterious t mutations per se but rather other genes linked to these mutations.This work was funded by a grant from the Research Council of Rutgers University.     

Responses of male mice to odors of females: Effects of T- and H-2-locus genotype

Male wild house mice (Mus musculus) were given a choice of odors of females whose T-locus genotype was +/ + or +/t. Males showed strong preferences for the odors of +/ + females. However, when males were tested with odors of recombinant females whose genotype differed at the T locus but which carried similar haplotypes at the H-2 locus, the preference for odors of +/+ females was not manifested. Consequently, differences in female odor production that are responsible for male odor preference are not due specifically to the female genotype at the T locus.This work was partially supported by NIH Grant HD R01 1997 and a BRSG Grant from Rutgers University.     

Multiple selection responses in house mice bidirectionally selected for thermoregulatory nest-building behavior: Crosses of replicate lines

Replicate high-selected, control, and low-selected lines were crossed at generation 46 of bidirectional selection for thermoregulatory nest-building behavior. Previous analysis of the lines at their limits had revealed multiple responses to uniform selection, where each of the four selected lines responded differently to reverse selection (Laffan, 1989). The reciprocal F₁ crosses showed significant heterosis for nest-building behavior compared to the contemporaneous generations of the parental lines. This pattern of heterosis in all three crosses is consistent with the finding that nest-building behavior in each of the four replicate lines had a different genetic basis, in spite of the phenotypic similarity between the two replicate lines in the high and low direction of nesting. This heterosis effect and the larger number of young weaned in all three crosses compared to their respective contemporaneous generation of the parental lines also support earlier findings that larger nests are closely related to fitness.     

Genetic mediation of infanticide and parental behavior in male and female domestic and wild stock house mice

Infanticide is a reproductive strategy found in many mammals, especially rodents. The proportion of male and female house mice (Mus domesticus) that are either infanticidal or noninfanticidal is strain specific and varies widely from stock to stock. Male house mice also show strain-specific variation in the behavioral mechanisms that inhibit infanticidal individuals from killing their own offspring. The adult offspring generated from reciprocally crossed CF-1 and Wild stock house mice were tested for their behavior toward newborn pups. In male CF-1xWild hybrids, the proportion of infanticidal and noninfanticidal males matched with their maternal phenotype, whereas female CF-1xWild hybrids exhibited a proportion of behaviors typical of the CF-1 phenotype, regardless of their mother's genotype. Our results suggest three conclusions: first, that infanticide is a highly labile and heritable behavior in both sexes; second, that there is a sex difference in the genetic substrate that regulates the inheritance of infanticidal behavior; and third, that selection pressures in male mice may operate independently on the mechanisms that promote spontaneous infanticidal behavior versus the mechanisms that inhibit infanticide.     

Nesting and Fitness: Lifetime Reproductive Success in House Mice Bidirectionally Selected for Thermoregulatory Nest-Building Behavior

To test the hypothesis that large, well-built, nests are an important component of fitness, we kept 12 mating pairs of two high-selected, two control, and two low-selected lines, selected for therrnoregulatory nest-building behavior, at 22 and 4°C with access to 10 g of cotton to build a nest, for a period of 180 days. Measurements included number of litters bom per family, number of young per litter born and surviving up to 40 days of age, nest type built by the parents, and weight gain of the young from weaning (20 days of age) to 40 days of age. In all lines the production and survival of offspring was substantially decreased at 4°C compared to 22°C, but the high-selected lines produced more and better-quality offspring, surviving up to 40 days of age at both temperatures compared to the control and low-selected lines. This indicates that thermoregulatory nest-building behavior and evolutionary fitness are closely associated.     

Circadian period in mice: Analysis of genetic and maternal contributions to inbred strain differences

Differences of approximately 25 min in the free-running period of a circadian rhythm for wheel-running activity were observed among four inbred mouse strains (Mus musculus). Two sets of reciprocal hybrid crosses among the strains showed approximately intermediate values for circadian period in one cross and dominance for a short period in the other. Neither set of crosses showed evidence of significant maternal effects on circadian period. These results indicate that the inbred strain differences in circadian period are imposed primarily by direct effects of allelic differences among the strains, rather than through maternally mediated mechanisms.This material is based upon work supported by the National Science Foundation under Grant PDF-8166034.     

Predicting relationships between psychological constructs and genetic characters: An analysis of changing genetic influences on activity in mice

Psychological constructs involving genetic characters can be of two types. The first type involves behavioral characters in which a score in a given direction should consistently confer a selective advantage on an organism across environments and age. Behavioral measurements taken in different situations should show low additive genetic correlations but similar patterns of directional dominance. A composite score summed across many measures representing the construct should show a high proportion of nonadditive genetic variance. Type 2 constructs involve behavior patterns in which high scores confer a selective advantage in some circumstances and a disadvantage in others. Behaviors representing such constructs should be characterized by high additive genetic correlations, suggesting a common set of genes influencing the behaviors at different ages or in different environments. The direction of nonadditive genetic effects should differ in accordance with optimal behavior levels in each test situation. Activity levels of housemice are shown to fit the model of a type 2 construct. Most measures used in human behavior genetics probably also reflect type 2 constructs.This work was supported by Grants GB-28017, BNS-7815366, and BNS-8121540 from the National Science Foundation.