UC Berkeley

Social behaviors are a fundamental part of mammalian life, and diverse species of mammals have evolved diverse social behaviors. An ongoing challenge in the field of neuroscience is to understand how genetic diversity gives rise to neural circuits that encode species specific social behaviors. Diversity in genetically encoded developmental mechanisms may promote divergence in neural circuits that encode specific social behaviors, but this hypothesis is difficult to test given our lack of understanding of detailed social behaviors, the neural circuits that encode them, and their developmental origins across genetically diverse organisms. Some major limiting factors include an over-reliance on a single inbred strain of mouse and use of social assays that limit the extent of interactions between animals as tools for understanding the neural encoding of social behaviors. Lastly, it is largely unclear how environmental factors determined by the specialized niches of diverse organisms interact with genetically encoded mechanisms to impact the development of circuits that encode social behaviors. In this dissertation, I present three studies that focus on 1) understanding social behavior at different timescales in genetically distinct strains of mice, 2) a genetically encoded neurodevelopmental mechanism that may contribute to social behaviors in mice and, 3) environmental regulation of brain development in meadow voles, a species with seasonally regulated social behaviors. In all, we identify an example of how recording free social behaviors at both sub-second and multi-day timescales is critical for understanding how subtle genetic variation contributes to differences in multiple subtypes of social investigations, including nose-to-nose and nose-to-rear contacts. We also describe the lipid composition of the fetal brain, and identify a molecule, prostaglandin D2, that is highly concentrated in the fetal brain and has strong potential to be released by macrophages to impact neural development and social behaviors. Lastly we report that social housing conditions and daylengths interact to shape the transcriptional profiles of single nuclei in the dorsal hippocampus in meadow voles, with primary impacts of housing on genes important for the function of oligodendrocytes, microglia, and astrocytes.