Sex, gender, sexuality, and sexual behavior are all distinct traits, but our understanding of their biological bases and their influence on health and disease lags behind their social impact. Our training grant takes a unique and integrative approach to this fundamental biological issue. We explore questions like: How do social stressors affect the genome and influence the balance between adaptive and maladaptive strategies of sociality or parenting in males vs. females? How does maternal antibiotic treatment affect offspring development, and what mechanisms make these carryover effects sex-specific? How do sex differences in immune responses bring about sex differences in health and disease?
History has shown that important insights into the basic mechanisms of reproduction and development can be gained by study of human and non-human model systems, as well as evolutionarily diverse non-model systems. The Program’s title, “Common Themes in Reproductive Diversity” is intended to focus attention on the universal challenge all animals must meet, to reproduce and provide for offspring, while also addressing the myriad ways in which animals accomplish these ends. Training focuses on three areas:
- Developmental contributions to reproductive behavior
- Origins and expression of differences among the sexes
- Interactions between sex, health, and disease
Developmental contributions to reproductive behavior
This theme approaches development broadly with research on how genetic and non-genetic factors, including parental, environmental, and epigenetic factors act across the lifespan to shape reproductive physiology and behavior.
Several Program Faculty focus on this theme, ranging from molecular and genomic to organismal:
- Delph studies the evolution of sexual dimorphism, from the perspective of both the selective forces driving it and the genetic components constraining it.
- Moyle studies the genetic mechanisms that contribute to pre- and post-fertilization successes and failures of reproduction.
- Nephew studies epigenetics, nuclear receptors, and steroid hormone action in human reproductive tissues.
- Moczek studies how environmentally regulated gene expression influences the differentiation of sex-specific traits (horns and genitalia) in young dung beetles.
- Demas studies the interaction of neuroendocrine and environmental influences on development.
- Rosvall and Smith explore hormonal and genomic mechanisms of the social behaviors that facilitate (or impede) successful reproduction, in birds and fish respectively.
- Alberts dissects the impact of the maternal environment and behavior on the physiology and social behavior of rat pups.
- Ketterson studies how developmental environments affect the timing of reproduction in adulthood.
- Hurley studies how early-life social isolation impacts reproductive vocal communication.
- Sengelaub focuses on the role of maternal licking in neuromuscular development and sexual behavior in rats.
- Garcia and Todd examine how environment and experience affect mate choice, formation and maintenance of relationships, reproductive strategies, and sexual behavior in humans.
Origins and expression of differences among the sexes
This theme addresses proximate mechanisms and evolutionary forces that guide the development and maintenance of sex differences in physiology, morphology, and behavior. Males and females can differ across multiple levels of biological organization: chromosomal and genetic composition; gene expression; gonadal physiology and gamete production; hormone production, release, and responsiveness; morphology; peripheral physiology; brain structure and function; cognition; and behavior. As repeatedly noted by NIH, understanding sex differences is critical for understanding human development and health, including sex-related variation in the quality and quantity of parental care, susceptibility to disease, and responsiveness to drugs and therapies.
Because sex-related variation is regulated at multiple levels of biological organization, the origin of sex differences is best addressed from multiple perspectives. Several Program Faculty devote their research to these topics, with expertise from the molecular to the evolutionary:
- Hahn and Moyle study how the evolution of sex-specific genes and sex chromosomes is linked to the origins of sexually dimorphic traits.
- Rosvall and Smith investigate neuroendocrine and genomic mechanisms of sex differences in adult reproductive, social, and parental behavior, and how these mechanisms evolve to yield variation in sex-specific behaviors.
- Demas, Hurley, Moczek, Ragsdale, Smith, Sengelaub, and Wellman address how hormonal effects on cellular physiology and anatomy induce sexually dimorphic morphology, physiology, and behavior at the organismal level.
- Demas, Rosvall, Sengelaub, and Smith study the roles of hormones in regulating developmental and adult plasticity in sex-specific reproductive behavior.
- Delph, Moyle, and Rosvall examine how differences in life history influence the evolution of variation across sexes.
- Garcia and Todd examine sex-related variation in human mate choice and sexual behaviors, and how this variation impacts reproductive and mental health across genders.
Interactions between sex, health, and disease
This theme addresses the inter-relationships among reproduction and immune function, microbiome, and disease transmission, sex differences in response to sickness or injury, as well as the larger issues of sexual and reproductive health.
Our training team contains leading international experts on this issue, including:
- Lively studies the dynamic population genetics of host-parasite interactions, and how such interactions underlie the evolution of sexual reproduction and select for variation and recombination in both hosts and pathogens/parasites.
- Demas studies trade-offs between reproduction, sickness, and immune responses, including how they vary among reproductive and non-reproductive cycles in a hamster model. Via collaborations with the Kinsey Institute, Demas has also leveraged this research to understand how vaginal immune parameters change across the reproductive cycle and interact with sexual behavior in humans.
- Ketterson studies disease transmission in migratory birds, including interactions among reproductive sex hormones, health, and disease.
- Nephew likewise studies sex steroid hormones, specifically their epigenetic effects, and his group conducts translational research developing epigenetic therapies for ovarian and breast cancers.
- Alberts, Demas, Newton, and Wellman study the effects of microbial communities on the development of behavior, including reproduction and parenting.
- Newton studies how microbial communities protect against environmental stressors in males and females in a wide range of invertebrate and vertebrate species.
- Wellman studies sex differences in the immediate and long-term effects of chronic stress and stress hormones on behavior.
- Sengelaub studies sex differences in steroid-mediated neuroplasticity and repair after injury.
- Barber’s studies the interplay between intimate relationships, attitudes/values/beliefs, and processes related to pregnancy.
- Garcia studies the role of intimate relationships in clinical populations
- Herbenick studies human sexuality, contraception, and sexually transmitted infections.