Meeting Abstract
Social behavior is among the most complex and variable of phenotypes. Optimal behaviors often depend on the strategies prevalent in a given population. In the case of the prairie vole, Microtus ochrogaster, a male transitions between a single and pair-bonded mating strategy when he is able to monopolize a female. The neuropeptide vasopressin plays a major role in the formation of such bonds, and the resulting strategies require coordination of brain regions involved in attachment, aggression, and memory. The expression of the vasopressin 1a receptor (V1aR) in the retrosplenial cortex (RSC), a brain region critical to memory, differs profoundly among prairie voles. Among males, RSC-V1aR predicts patterns of space use and sexual fidelity. We identified two alleles that drive differences in RSC-V1aR: a high allele that is favored in the context of intra-pair paternity, and a low allele that is favoring during extra-pair paternity. The alleles differ in several single-nucleotide polymorphisms located within a putative enhancer. The low-expressing allele contains significantly more CpG sites within this enhancer. Manipulations of developmental environments reveal that the low allele is more sensitive to both methylation and demethylation. Together the data suggest that the high allele shapes socio-spatial memory to promote mate-guarding, and is largely insensitive to developmental environment; the low allele, in contrast, seems to promote scarmble competition, but allows epigenetic modification of gene expression and behavior. We hypothesize that this represents an example of neuroendocrine reaction norms mediated by the abundance of CpG sites within a regulatory sequence.
