Cynthia Jordan - US grants

9309856 Jordan During normal development, adult patterns of synaptic connections are established through an elimination of excess neural connections. For example, in newborns, muscle fibers receive innervation from several different motoneurons. By the time the mammal has matured into adulthood, muscle fibers are each typically innervated by only a single motoneuron. Dr. Jordan's research program seeks to understand the cellular and molecular bases of synapse elimination. Her model is a a relatively simple neuromuscular system, namely the perineal levator ani muscle and its innervating motoneurons located in the spinal nucleus of the bulbocavernosus. Studying synapse elimination in this system offers the significant advantage that this mechanism can be regulated by steroid hormones. Androgen treatment during a specified period of development permanently prevents some synapse elimination in this system. Thus, androgens are a naturally occurring factor that influences the development of the central nervous system. Dr. Jordan will use steroid hormones as a tool for the control and manipulation of synapse elimination. Information about where androgen acts to prevent this loss is necessary for directing further experiments aimed at identifying the underlying mechanisms. In addition, she will examine the mechanisms that initiate the onset of synapse elimination. Dr. Jordan will explore the possibility that it is the electrical uncoupling of the neurons that underlie the selective stabilization and maintenance of synapses. Information gained about the factors controlling this crucial developmental event in the neuromuscular system could be applied to neuronal populations in the brain that undergo similar synaptic alternations due to either normal or pathological processes. ***

One of the main signals driving sex differences in behavior are androgens produced by the male tests. Androgens promote the expression of various sex-specific behaviors by interacting directly with the nervous system where they bind to specialized receptor proteins in cells. The nervous system is comprised of two main cell types, neurons and glia. Neurons carry information and control behavior and glia have a more supportive role. There is no doubt that androgens directly affect neurons, since these cell have androgen receptors (ARs). However, recent evidence reveals that glia also have ARs, suggesting that androgens may also exert direct effects on gila. Dr. Jordan has found that Schwann cells, glia which ensheath axons in peripheral nerves, have ARs. This novel finding has many implications. For example, androgens keep neurons and synapses alive, even some neurons that lack ARs. The effect of androgens on neuronal survival is likely mediated via neurotrophic substances. Because Schwann cells make neurotrophic substances, androgens may act on ARs in Schwann cells to increase their productive of neurotrophic substances which in turn enhance neuronal and synaptic survival. The experiments described in this proposal will further characterize the presence of ARs in peripheral nerve of adult male and female rodents with overall aim of understanding the role of ARs in regulating neural structure and function. Immunocytochemistry, reverse transcriptase-polymerase chain reaction, and in situ hybridization will be used to identify and quantify which cells in peripheral nerve express the AR gene and protein.

DESCRIPTION (provided by applicant): Testicular steroids exert effects throughout the body, regulating cell physiology and structure in numerous target organs. For example, androgens have anabolic effects on skeletal muscle, and also affect the nervous system, which among other things, determines sexual phenotype of the brain and regulates behavior. In one such neuromuscular system in rats, the sexually dimorphic SNB system, some androgen effects on neurons are mediated through skeletal muscles. For example, androgens act on the muscle in development to ensure that motoneurons survive and to cause those same motoneurons to extend dendrites in adulthood. Androgens also work directly on muscle in development to ensure its survival and to determine its overall size in adulthood. However, it is not known what cells in muscle have androgen receptors (ARs). Answering this question represents the first step toward understanding how androgens work in muscle to influence the muscle directly and the motoneurons indirectly. Immunocytochemistry (ICC) will be used to identify the cells in rat muscles that express ARs, comparing the levator ani (LA) to the extensor digitorum longus (EDL), which differ in their sensitivity to androgens. ICC will also be used to characterize the role of androgens and innervation on AR expression; both influence the androgen sensitivity of skeletal muscles. Reverse transcriptase polymerase chain reaction (RT-PCR) will also be used to quantify AR message. We will test directly the role of ARs in muscle fibers by transfecting in vivo AR genes into AR-deficient mutant muscle fibers. Because muscle wasting occurs in Kennedy's Syndrome (caused by a mutation in the AR gene) and in amyotrophic lateral sclerosis (ALS), these studies aimed at identifying and understanding the mechanisms by which androgens spare motoneurons and muscle fibers from death, and promote their growth in adulthood, may suggest new therapeutic measures for individuals suffering from such pathologies. This path holds particular promise, since the human homologue to the rodent SNB is completely spared in individuals that die of ALS. This finding suggests a potentially important relationship between ARs in muscle and the growth and/or demise of the muscle and its motoneurons.

[unreadable] DESCRIPTION (provided by applicant): Androgens influence the survival and growth of a neuromuscular system, the spinal nucleus of the bulbocavernosus (SNB) and its target muscles, the levator ani (LA) and the bulbocavernosus (BC). Proposed experiments will test whether LA/BC muscle fibers are direct cellular targets for androgens. Focus will be on LA/BC muscle fibers as prime mediators of androgenic influences on the SNB system because 1) androgens act directly on LA/BC muscles to regulate their survival and growth, and the survival and growth of SNB motoneurons and 2) androgen receptors (ARs) are enriched in muscle fibers of the LA/BC compared to other skeletal muscles. Proposed experiments will utilize two newly created transgenic mouse models that either over or under express ARs in their muscle fibers. These two models will be used to evaluate whether ARs in muscle fibers are necessary and/or sufficient for androgens to rescue the SNB system from death in development and promote expression of calcitonin gene-related peptide by SNB motoneurons in adulthood. Transgenic males will be compared to controls males (wild-type males and/or males that have a dysfunctional AR gene) and standard cellular approaches will be applied to answer these questions. Finally, males in some transgenic lines that overexpress ARs in muscle fibers show a progressive, late-onset neuromuscular degenerative disease that mimics Spinal Bulbar Muscular Atrophy (SBMA), a neurodegenerative disease in humans caused by a mutation in the AR gene (expansion of CAG repeats). SBMA afflicts primarily men in mid-life. Some proposed experiments are aimed at characterizing the emergent phenotype and the underlying pathology of this disease, and its ligand-dependence using behavioral, cellular and molecular methods. Relevance: Despite the essential role motoneurons have in all aspects of human life, motoneurons are susceptible to disease, and undergo selective demise in diseases such as Spinal Bulbar Muscular Atrophy (SBMA) and Amyotrophic Lateral Sclerosis (ALS). As part of the normal course of development, androgenic hormones prevent some motoneurons from dying and curiously, these same motoneurons are selectively spared in SBMA and ALS. We propose to study transgenic mouse models that have an altered expression of androgen receptors in skeletal muscle fibers to better understand how hormones regulate the survival of motoneurons. [unreadable] [unreadable]

There continues to be a shortage of young people, particularly young people from under-represented groups, entering careers in basic research. One strategy to boost these numbers is to provide programs that discuss science generally. However, such programs suffer by being so broad in subject matter that they might not engage students' interest in scientific problems, and being so vague in terms of what it's like to be a scientist that the students have only a theoretical notion of what such a career entails. An alternative strategy is to identify a particular field of study, find students who have already shown some interest in that particular field, and then bring them together to give them hands-on experience in a lab and ample social opportunities to meet and talk to active scientists in that field. In partnership with a consortium of universities, including several traditionally African-American undergraduate colleges, we will bring 10 undergraduate students from around the country to our campus for a one-week intensive course in behavioral neuroendocrinology: the study of the influence of hormones on behavior, and the influence of behavior on hormone secretion. We will identify the students by soliciting from laboratories engaged in behavioral endocrinology research. In our inaugural session offered last year, we received over 50 strong candidates for 8 positions. In order to capitalize on this learning experience, and to give the students a deeper understanding of the field, as well as a sense of what life as a scientist is like, we will send these students to the subsequent meeting of the Society for Behavioral Neuroendocrinology (SBN). At the SBN meeting, the students have the opportunity to have "lunch with the professors" from yet other universities and discuss current and future scientific endeavers. We are requesting funds to pay the airfares, registration and lodging for these undergraduates for both the short course on campus and the SBN meeting thereafter, as well as funds to bring neuroendocrinologists from other campuses to serve as instructors. What is unique about this experience is the hands-on laboratory training, the intensive social interaction with scientists, from half a dozen different universities, before and during a professional meeting, and the exposure to a wide range of working graduate students and postdoctoral fellows in the field. Bringing together an mixture of students, emphasizing students from under-represented groups, who have expressed interest in a career in science, will increase the strength and the diversity of the applicant pool in this area of science nationwide. Our goal is to let these students see how intellectually and socially satisfying a career in science can be so that more of them choose this career.

PROJECT SUMMARY A major risk factor in the vulnerability to immune disorders is biological sex. In some of the most prevalent immune disorders such as allergy/anaphylaxis, autoimmune disease, and chronic pain disorders, females are at increased risk. Adult sex hormones, such as estrogen, may explain some of the sex differences; however, that many immune disorders exhibit a sex bias in prepubertal children challenges this concept. Our recent published and preliminary studies have uncovered sex differences in the mast cell that may explain female vulnerability or male resilience to many immune disorders. Mast cells are innate immune cells that play a central role as effector cell and orchestrators of the immune response. The fact that many mast cell-associated disorders (Allergy, auto- immune, chronic pain, irritable bowel syndrome) exhibit a sex bias in both childhood and adulthood positions the mast cell as a novel regulator of sex differences in immune diseases. Specifically we have shown that female mast cells possess an increased capacity to synthesize, store and release potent mast cell mediators including histamine, serotonin, proteases, etc. In animal models of IgE-mediated anaphylaxis and psychological stress, female animals exhibited enhanced release of mast cell mediators and more severe pathophysiologic and clinical disease, similar to humans. Moreover our recent preliminary data showed that sex differences in mast cells emerge early in development prior to puberty and thus may explain sex differences observed in children. When and how sex differences in the mast cell increase female vulnerability to immune disorders is unknown. Based on preliminary data, we hypothesize that sexual differences in mast cell phenotype and immune-related disease susceptibility is established early in life by perinatal androgens. In this R21 proposal, we aim to establish the role perinatal sex hormones in sex differences in the mast cell and susceptibility/resiliency to later life immune diseases. Toward this goal, we will 1) identify when in development sex differences emerge in the phenotype of mast cells and 2) identify the contribution of perinatal androgens in mast cell sex differences and disease susceptibility. The exploratory studies proposed in the grant application will represent a major paradigm shift in the understanding of sex and mast cell related immune disorders.

PROJECT SUMMARY Exposure to early life adversity (ELA) during critical periods of prenatal and postnatal development is an important risk factor for the later life onset of highly prevalent gastrointestinal (GI) diseases, including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). The precise mechanisms linking ELA and GI disease susceptibility are unknown and thus management and therapeutic targets and biomarkers are lacking. Our studies using a porcine model demonstrated that ELA alters the normal course of GI development resulting in lifelong intestinal barrier dysfunction or ?leaky gut', neuroimmune dysregulation and increased GI disease that recapitulates much of the pathophysiology and clinical features of human stress-related GI disorders. We recently identified two factors associated with ELA-induced GI disease susceptibility and severity in adulthood: (1) heightened and persistent intestinal mast cell hyper-activity and (2) biological sex with females at increased risk and males protected. Furthermore, we have identified novel sex-differences in the mast cell phenotype in that mast cell from female animals exhibit enhanced synthesis storage and stress-induced release of mediators such as histamine, proteases and serotonin which have known roles in GI neuroimmune disorders. Our hypothesis is that mast cells and biological sex interact to organize the development of GI barrier and neuroimmune systems, consequently determining the lifetime risk to disease following exposure to ELA. We have designed three specific aims to accomplish this objective. Aim 1 will test the hypothesis that hyper-activation of GI mast cells during early postnatal development lead to GI barrier and neuroimmune dysfunction in adulthood. Aim 2 will test the hypothesis that the heightened vulnerability of females to ELA-induced GI disease depends on androgens acting during early development. Aim 3 will test the hypothesis that ELA and perinatal androgens program mast cells, via epigenetic and transcriptional mechanisms, resulting in mast cell hyperactivity which drives GI barrier and neuroimmune dysfunction into adulthood. Together, the studies proposed in the grant application are expected to result in a major paradigm shift in the understanding the origins of ELA-induced and sex-biased GI neuroimmune diseases which could ultimately unveil new therapeutic targets to protect the GI system during vulnerable periods of stress and to therapeutically modulate adult diseases in both sexes.