David C. Page has been a pioneer in the field of mammalian sex determination for 20 years. He conducts studies of the sex chromosomes and their roles in germ cell development, with special attention on the function, structure, and evolution of the Y chromosome. Dr. Page’s laboratory, in conjunction with colleagues at Washington University, reconstructed the evolution of today's X and Y chromosomes from an ancestral pair of autosomes that existed 300 million years ago. They discovered that most Y chromosome genes are members of Y-specific families that are primarily expressed in testicular germ cells, and exist as mirror-image pairs on massive palindromes that are sites of frequent gene conversion. Thus, the male-specific chromosome is intensely recombinogenic despite the absence of conventional crossing over. Dr. Page’s laboratory also discovered and characterized the most common genetic cause of spermatogenic failure in humans. He is now turning his attention to the question of germ cell sex determination in mammals and to the development of the ovary.

2005 Symposium Topic: Genes, gender and germ cells

Allan C. Spradling studies germ cells throughout their life cycle, from fertilized eggs to germline stem cells in the adult. Several years ago, Dr. Spradling and his colleagues used lineage tracing and molecular techniques to identify a germline stem cell population in the Drosophila ovary. Exploring the interactions between stem cells and their specialized cellular microenvironment created by the somatic niche led to a detailed molecular model for the control of stem cell maintenance throughout adult life and oocyte differentiation. The experimental beauty of these studies and the molecular insight gained rapidly established the fly germline stem cell system as a model for other stem cell studies. In addition to defining germline stem cells, Dr. Spradling is also interested in the cellular and molecular mechanisms underlying oocyte differentiation in both flies and mice. By suggesting that oocytes may selectively remove damaged organelles such as mitochondria that may otherwise be detrimental for the success of the next generation, his studies address one of the most intriguing questions of germ cell development.

2005 Symposium Topic: Stem cells searching for a meaningful relationship

Larry Young is interested in the molecular, cellular and neurobiological mechanisms that underlie the regulation of social behavior. Specifically, much of Dr. Young's research focuses on the role of oxytocin, vasopressin, CRF and their receptors in the regulation of social recognition, social bonding, and more recently, the consequences of social loss. His research utilizes both transgenic and knockout mice, as well as monogamous voles, and makes comparisons with primate species when possible.

2005 Symposium Topic: The neurobiology of the pair bond

Lique Coolen’s long-term research goal has been to understand how the brain regulates motivation and reward using sexual behavior in rodents as a model system. Recently her laboratory has identified a population of spinal neurons that play a pivotal role in the control of ejaculatory reflexes. The cell-specific lesions of these cells completely abolish ejaculatory reflexes. Moreover, these spinal neurons have anatomical connections to other spinal regions where they control the coordinated autonomic and motor outflow necessary for ejaculation. In addition, this population of spinal neurons has projections to the thalamus where sensory signals specifically related to ejaculation are conveyed. In turn, the thalamus projects to various brain regions that may contribute to the rewarding or reinforcing properties of ejaculation. Recently, they have shown that sexual experience results in functional, morphological, and transcriptional alterations of the mesolimbic system that plays an important role in regulation of motivation and reward. Dr. Coolen and her laboratory hypothesize that this plasticity may contribute to the reinforcing properties of sexual behavior.

2005 Symposium Topic: The neurobiology of sexual reward

Ed Kravitz and his laboratory have been studying aggression using a lobster model system for over 20 years. Recently, with a sequenced genome available and with powerful methods available for manipulating genes, the focus of interest of his laboratory has shifted to studies of aggression in fruit flies. In general, it is not well known that fruit flies fight, even though the first mention of fighting between pairs of male flies dates back to Sturtevant in 1915. Even fewer citations exist in the literature suggesting that pairs of female Drosophila fight also. Dr. Kravitz and his laboratory have carried out a quantitative analysis of fighting behavior between pairs of male and female fruit flies and they observe that some of the behavioral patterns (modules) seen during fights are similar in male and female fights, some are unique to females and some are unique to males. They have been manipulating the expression of genes of the gender determination pathway (transformer and fruitless) regionally and globally in fly brains addressing the issue of whether they can transfer female patterns of aggression to male brains and/or male patterns to female brains.

2005 Symposium Topic: The modularity of behavior: genetics and the patterns of

Barbara Meyer’s laboratory uses the nematode C. elegans as a model to study fundamental aspects of chromosome dynamics and development. The laboratory’s recent focus has been on understanding how chromosome architecture and segregation are controlled during meiosis and mitosis, how the sex chromosome is regulated to normalize gene expression between the two sexes, and how choices are made between different cell fates during development.

2005 Symposium Topic: Sex and repression

Catherine Dulac’s laboratory explores how pheromones are sensed and induce specific behaviors. Pheromones have evolved in all animal phyla to signal the sex and the dominance status of animals and to promote mating and social rituals among conspecifics. In mammals, pheromones are primarily detected by the vomeronasal organ (VNO). The Dulac lab has identified several hundred candidate pheromone receptors, uncovered the wiring diagram of VNO fibers, and generated mutant mice that lack VNO function. These animals display courtship and mounting behavior indiscriminately toward both males and females. These data contradict the established notion that VNO activity is required for the initiation of male-female mating behavior in the mouse and suggest instead a critical role in insuring sex discrimination.

2005 Symposium Topic: Molecular architecture of pheromone sensing in mammals