Kimberly A. Rosvall, Ph.D. - US grants

DESCRIPTION (provided by applicant): The overarching goal of the research described in this proposal is to characterize the degree of integration of neuroendocrine mechanisms of behavior at multiple levels of biological organization, from gene/protein to hormone to behavior, among individuals and between sexes. The proposed research will probe co-variation among these levels of organization, with a focus on aggression and sex steroid hormones. Previous research provides a firm understanding of steroid action, but leaves significant uncertainty about how these levels of organization interact with one another within an individual, leading to a specific behavioral outcome. In particular, surprisingly little is known as to whether the expression of steroid hormone-binding molecules in the brain predicts variation in behavior at the level of individuals. Also not clear is whether the mechanisms that lead to individual variability in behavior within a sex are shared between the sexes, i.e. the degree to which males and females use similar or different mechanisms to produce outwardly similar behaviors. The proposed study species is a songbird, the dark-eyed junco (Junco hyemalis), which is ideal owing to extensive existing knowledge of the effects of testosterone (T) on behavioral variation among individuals and between sexes. The research will employ both experimental and observational approaches by quantifying both protein and mRNA for steroid-sensitive neural targets (androgen receptor, AR;estrogen receptor, ER;and the enzyme aromatase, ARO, which converts T to estradiol, E2) across a diversity of behaviorally relevant neural loci. Collectively, a neural systems approach is used to address two specific aims: (1) To identify patterns of co-variation between an individual's degree of aggressiveness, its level of circulating T and E2 and its neural expression of AR, ER and ARO. This aim is achieved by assaying aggression in free-living subjects and comparing their behavior to circulating hormone levels and to mRNA for neural steroid targets, using quantitative PCR. (2) To compare whether males and females use similar steroid-mediated mechanisms of aggression. This aim is achieved by using data from the first study to contrast target-behavior relationships between males and females. A second study dives deeper, using immunocytochemistry to identify sex differences in the specific neural circuitry in which one steroid target (ARO) mediates aggression. ARO-mediated aggression will be quantified by co- localizing ARO with the immediate early gene product Fos following an aggression trial. The proposed research will address a significant unknown in behavioral neuroendocrinology (individual variation), and then extend this novel approach to sex comparisons. By filling these key knowledge gaps, this research will illuminate fundamental neuroendocrine mechanisms of behavior. It will thus contribute to a foundation of basic knowledge needed for future research on neuroendocrine factors affecting steroid-mediated health issues, including sex and individual differences in the propensity for behavioral disorders with high levels of violence/ aggression (e.g. ADHD, conduct disorder, etc.), or improved treatments of related neural deficiencies. PUBLIC HEALTH RELEVANCE: By identifying the genetic and cellular factors that underlie variability in overt aggression at the individual level and comparing these neuroendocrine mechanisms between males and females, this research fills unresolved knowledge gaps about basic biobehavioral mechanisms. These studies thus lay the groundwork for future advances in the individualized treatment and prevention of a number of steroid-mediated behavioral disorders affecting children and adults of all ages. Likewise, the identification of factors that differentially promote aggression in males and females will increase understanding of fundamental sex differences in neurobiology and behavior, and could be applied to future work on the causes/treatment of known sex differences in aggressive tendencies or other hormone-mediated health issues in men and women.

DESCRIPTION (provided by applicant): Social competition is ubiquitous in both animal and human life, and the threat from a competitor typically induces a systemic surge in the steroid hormone testosterone. While past research demonstrates clear connections among social challenges, testosterone and a suite of physiological and behavioral effects, the molecular mechanisms underlying these phenotypic changes are poorly understood. Generating an appropriate organismal response to social challenges requires large scale coordination of behavior and physiology (e.g. changes in aggression, pain tolerance, and metabolism), yet the transcriptomic mechanisms by which brain and body act together to produce a coordinated response to social challenges are unclear. The long-term goal of the proposed research is to determine how steroid hormones serve to link brain and periphery in genomic and behavioral responses to environmental contingencies. The working hypothesis is that social challenges, and their associated testosterone surges, prime individuals for success in future competition, favoring greater mobilization of energy reserves, heightened response to injury or inflammation, and greater spatial and sensory capabilities, all at the expense of self-maintenance. The objectives of this particular application are to identify how gene transcription is altered by aggressive social interactions, and to characterize how the environmental effects of a social challenge differ in brain and periphery, while engendering a coordinated organismal response to social instability. The subject is a well-studied songbird in which social challenges lead to a systemic surge in testosterone, and the effects of testosterone on many aspects of behavior and physiology are well characterized (aggression, immune function, stress, activity, etc.). By employing emerging genomic techniques, including gene set enrichment and network co-expression analyses, the proposed research will identify the effects of (1) acute social challenges and (2) persistent social instability on gene transcription, relative to unchallenged control animals. These data will reveal gene families, hubs of connectivity within gene networks, and neural and peripheral tissues that are particularly prone to socially induced plasticity. Patterns of co-variation among tissues will further reveal the precise molecular mechanisms by which social challenges prime the brain and body for a coordinated response to social instability. Knowledge of how social stressors derail normal healthy organismal function can be applied to a range of hormonally and socially induced human health issues (e.g. reproductive health, behavioral disorders of high aggression, etc.), where insights to be gained by co-discussion of social environment, brain, and periphery have yet to be fully realized. PUBLIC HEALTH RELEVANCE: Because social stressors are pervasive in human and animal life, and the proposed studies will identify the genes, brain regions and peripheral organs that are particularly susceptible to either acute or persistent socially stressors, this research fills unresolved knowledge gaps about the molecular mechanisms by which socially challenging experiences engender physiological and behavioral effects. Social competition and the hormonal changes that coincide with social challenges have been linked with a variety of public health issues in humans (e.g. bullying, ADHD, conduct disorder, cardiac and reproductive health, etc.). Thus, the proposed research, which identifies the effects of social instability on organism-wide gene expression, will lay the groundwork for advances in developing new targets for the treatment and prevention of a number of behavioral and physiological disorders affecting children and adults of all ages.

Non-technical Abstract:

Social competition among males is thought to induce a coordinated set of behavioral and physiological responses that are adaptive for continued success during competition. It is far less clear how these processes operate in females, despite emerging evidence that female competition is widespread and beneficial in the animal kingdom. This research will identify whether and how social competition "primes" (or adaptively prepares) females for future competition. The subject is a cavity-nesting female songbird, the tree swallow, for which social challenges from rivals pose a very real threat to survival and reproduction. Using experimental manipulations that generate competition in the wild, this research will investigate how social competition alters female aggression, maternal care, and immune function, including tools and approaches that connect multiple levels of biological organization, from gene expression, to behavior and physiology, to reproductive fitness. Research on female aggression is an excellent platform for outreach to women and girls in science, and this will be highlighted in hands-on modules for several community organizations near Indiana University's campus, with an emphasis on the plight of cavity nesting birds and the effects of habitat loss on their behavior. The development of an interactive data-logging nestbox features prominently in these efforts. This project will also provide unique training for undergraduates in animal behavior, including field, lab, and programming skills, public speaking, ethics, and critical thinking. The primary avenue for training is a summer undergraduate research program that targets groups underrepresented in the sciences.

Technical Abstract:

The overall goal of this research is to determine how social challenges prepare females for future social instability, particularly how brain and periphery are coordinated in their phenotypic and transcriptomic responses. The working hypotheses are that social challenges prime females for success in future competition, favoring greater aggression at the expense of parenting and self-maintenance, and that these effects are coordinated by tissue-level changes in specific G protein-coupled receptor signaling systems that are not as costly to females as the male-typical social modulation of testosterone. Using experimental manipulations that generate true social instability in the wild, this research will (1) quantify how social instability alters aggression and maternal care, (2) quantify how the social environment affects inflammatory function, as an integrated measure of immune system readiness that may be relevant during competition, and (3) identify and experimentally perturb socially sensitive gene networks in neural and peripheral tissues, including one tissue that can be re-sampled without euthanasia (blood). This research is therefore an essential step in organismal biology's goal of predicting responses to diverse environmental challenges, and it will advance the development of broadly applicable models of behavioral plasticity that integrate function with mechanism. A whole-organism approach will allow new perspectives on phenotypic and genomic flexibility, where insights to be gained by joint consideration of brain and periphery have yet to be fully realized. These studies offer an extraordinary opportunity for substantive advances in understanding the mechanisms, phenotypic consequences, and adaptive significance of organismal responses to ecologically relevant behavioral challenges.