Lara Carroll

Email: LSC3@.utah.edu

Female mice use odor cues to select mates possessing a dissimilar MHC type (Major Histocompatibility Complex) from their own. But which genes within the enormous MHC region control individual odor? We think that classical MHC antigen presenting genes are the likeliest candidates for controlling odors. These highly polymorphic genes encode the MHC peptide binding site and thereby control which antigens (infectious and otherwise) can be recognized and presented by an individualís MHC molecules to her immune system. Individuals with different classical MHC genes recognize and bind different antigens, resulting in differential susceptibility and resistance to various infectious agents. Mating with an MHC dissimilar mate begets offspring with greater MHC diversity, potentially increasing their disease resistance. The differential binding properties of classical MHC alleles could result in different metabolites or metabolic byproducts, producing odor differences among MHC dissimilar individuals. So for any vertebrate surrounded by pathogens and parasites, the ability to detect and prefer MHC odor differences in potential mates could ultimately increase lifetime fitness.

I am currently working with three strains of laboratory mice that differ from one another at only one classical MHC locus (bm mutants). I am testing whether odor differences among these mutants are detectable by untrained mice. Ultimately, I will test whether females prefer to mate with males that are genetically different by only a single classical MHC gene.

Another project I am currently undertaking is to characterize MHC genes in populations of wild house mice and correlate these findings with parasite loads. Although house mice are the most widely researched animal model for medical science, very little is known about the behavior and biology of this animal in the wild.

I originally came to graduate school to study desert lizards. My preliminary work here involved characterizing the mating system of sagebrush lizards (Sceloporus graciosus) in the Utah desert. From genetic studies on birds, it is clear that nestlings are not always fathered by the putative male parent but often by an extra-territorial male. I am testing whether this pattern exists in sagebrush lizards as well. Because lizards offer no parental care to their young, male (genetic) quality may be best represented by the territory he is able to defend. Females on high quality territories may therefore be more likely to mate with their territorial male than females on low quality territories. Older females tend to settle on the best territories, and older males tend to obtain the best territories, so I expect mate fidelity to correlate positively with both female and male age. I am currently developing microsatellite primers to use for a PCR based genotyping system. This will allow me to determine paternity for a population of sagebrush lizards in the Stansbury Mountains.