29th Annual Meeting of the American Society of Andrology, 2004
The 29th Annual Meeting of the American Society of Andrology was held in Baltimore, Maryland, April 17-20, 2004. There was significant international participation in the meeting, including abstract presentations from investigators representing 21 countries in addition to the United States and Canada.
The ASA Postgraduate Course and the Andrology Laboratory Workshop preceded the Annual Meeting on Saturday, April 17. The Postgraduate Course, "Men’s Health: On the Horizons of Andrology," was chaired by Wylie Hembree and included presentations on osteoporosis, transsexualism and abuse of anabolic steroids. Steven Schrader chaired the Andrology Laboratory Workshop. This "Sperm Morphology Workshop," was a laboratory-based class with "hands-on" training in the microscopic assessment of sperm morphology according to classification methods currently used in clinical laboratories.
The program for the Annual Meeting featured eight plenary lectures and five symposia. The meeting opened with the Serono Lecture, presented by Judith Kimble from the University of Wisconsin - Madison. Her talk, "RNA-Binding Proteins Regulate Germline Development and Stem Cell Maintenance," highlighted the central role that post-transcriptional regulation plays in these developmental processes. Her studies identified the somatic niche and determined that it maintains germline stem cells in the undifferentiated state through the Notch signaling pathway. Downstream of Notch signaling, RNA regulators modulate several important transitions, including the decision between mitosis and entry into meiosis and the switch from spermatogenesis to oogenesis in C. elegans hermaphrodites. These RNA regulators may have conserved functions in development and cell cycle control since orthologs have been identified in several species, including mammals.
Myles Brown (Dana-Farber Cancer Center Institute and Harvard Medical School) gave the American Urological Association Lecture on "Selective Steroid Receptor Modulators." The recruitment of coactivators and corepressors plays a central role in the dynamic regulation of gene transcription by steroid receptors. Dr. Brown emphasized the importance of these coregulators in identifying new endocrine therapies that are targeted to specific cell types. He provided evidence that coregulators can be differentially recruited to specific regulatory regions of target genes and can selectively mediate agonist-induced degradation of estrogen receptor a. Understanding cell type- and promoter-specific differences in coregulator recruitment and action may facilitate the development of new therapies for both breast and prostate cancer.
The Women in Andrology Lecture on "Membrane Fusion at Fertilization" was given by Diana Myles (University of California - Davis). Her studies have systematically assessed the roles of several proteins proposed to be essential mediators of gamete fusion. Although multiple ADAMs on the sperm surface participate in fertilization, recent studies suggest that they do not play important roles in membrane fusion. On the egg surface, the tetraspanin CD9 is essential for gamete fusion and GPI-anchored proteins also appear to be required. Analyses of specific functional domains of CD9 and the assessment of other candidate proteins on the surfaces of sperm and eggs are providing a clearer model for the molecular events of gamete fusion at fertilization.
Robert Viger (Université Laval) presented a lecture on the "Role of GATA Transcription Factors in the Control of Testicular Gene Expression and Function." Three members of this family of zinc finger DNA-binding proteins (GATA 1, 4 and 6) are expressed in the testis. Dr. Viger’s studies determined that these factors regulate multiple genes involved in Sertoli and Leydig cell function, and that GATA activity plays important regulatory roles in male sex determination, testis development and steroidogenesis.
In his lecture "Basic and Clinical Aspects of Androgen Replacement Therapy," Shalendar Bhasin (Charles Drew University) presented four case studies of men with low testosterone and evaluated the relative merits of androgen replacement in each case. He indicated that the efficacy of testosterone replacement has been clearly demonstrated for men with hypogonadism. However, Dr. Bhasin stressed the need for randomized controlled trials to further evaluate the effects of testosterone replacement for erectile dysfunction, sarcopenia associated with chronic illness, or for older asymptomatic men with low testosterone levels.
Sylvie Breton, Ph.D., (Massachusetts General Hospital and Harvard Medical School) gave a lecture on "Establishing an Optimal Environment for Sperm Maturation in the Epididymis." Her work established the importance of vacuolar H+-ATPase (V-ATPase) in acidifying luminal fluid in the epididymis to an appropriate pH for maintainance of sperm quiescence. Proton secretion is regulated by recycling of V-ATPase between intracellular vesicles and the apical plasma membrane. In her work to define the molecular details of the acidification mechanism, Dr. Breton has identified soluble adenylyl cyclase and gelsolin as mediators of increased V-ATPase recycling in response to alkaline luminal pH and bicarbonate.
The International Lecture was given by Bernard Jégou (Université de Rennes I). His talk highlighted several components of the "Anti-Infectious Defense System in the Male Reproductive Tract" that provides protection against drugs, pathogens and other stressors. Multidrug resistance genes, which play a central role in drug efflux and confer resistance to a variety of chemotherapeutic drugs, are expressed in all somatic cells in the testis and in late spermatids. Dr. Jegou identified antiviral defense mechanisms in the testis, including the production of interferons and interferon-induced antiviral proteins by Leydig cells, macrophages, peritubular cells, Sertoli cells and spermatogonia. In addition, he determined that multiple antimicrobial defensins are expressed in the testis and epididymis, including several novel b-defensins. These multiple strategies are rapidly advancing our understanding of defense systems in the male reproductive tract.
Martin Dym (Georgetown University) gave a lecture on "Novel aspects of spermatogonial stem cells." He outlined procedures for the isolation of stem cells from juvenile testes using immunomagnetic beads and highlighted analyses of genes that are expressed by these spermatogonial stem cells. SAGE analyses detected the restricted expression of numerous transcripts in spermatogonia compared to later stages of spermatogenesis, with 10% representing novel genes. Dr. Dym reported on the generation of germ cell lines and efforts to induce differentiation in culture to produce "synthetic sex cells." Differentiation to haploid stages has been achieved, and these cells have been used for intracytoplasmic injections of eggs to produce morula-stage embryos.
Drug Discovery and Development was the topic of Symposium I. M. Cristina Meriggiola (University of Bologna) began the session with a talk on "Progress in Hormonal Male Contraception." Although testosterone-only regimens are effective in producing azoospermia in most Asian populations, they are less effective in suppressing sperm production in Caucasians. Dr. Meriggiola determined that androgen-progestin combinations are more effective in achieving azoospermia and compared a number of combination formulations that have been used in clinical trials. She stressed the need for further studies to develop better formulations, including noninjectables and long-acting hormones, to increase choices and improve the long-term safety of hormonal contraceptives for men. David Rotella (Lexicon Pharmaceuticals) presented a talk on "Phosphodiesterase 5 Inhibitors for Treatment of Erectile Dysfunction: Is There Room for Any More?" He reviewed the risk factors for erectile dysfunction and gave a detailed comparison of the three PDE5 inhibitors that are currently on the market. All three have efficacies in the 80-85% range, but differ in their potency, selectivity, duration of action, and usefulness for men with other health problems such as cardiovascular disease or diabetes. New PDE5 inhibitors that are now in phase I clinical trials may provide alternative therapies for erectile dysfunction and potentially for other disorders. Greg Kopf (Wyeth Research) discussed "Small Molecule Screening in the Drug Development Process." He described the typical timeline and cost of bringing a new drug to market, and indicated that many factors affect the development process, including unmet need, degree of innovation, nature of the target, and desired therapeutic endpoint. He also outlined strategies for the identification of new targets and for high throughput screening of large libraries of compounds.
Symposium II focused on the Regulation of Sperm Function and Fertilization. Pablo Visconti, (University of Massachusetts - Amherst) gave the first talk on "Signal Transduction Pathways during Capacitation." The process of capacitation occurs in the female reproductive tract and confers fertilizing ability on the sperm, including changes in the sperm head that lead to the acrosome reaction and changes in the sperm tail that prepare the sperm for hyperactivation. Capacitation-associated events include efflux of membrane cholesterol, increases in intracellular cyclic AMP, membrane hyperpolarization, calcium influx and tyrosine phosphorylation of a number of sperm proteins. Dr. Visconti presented evidence that capacitation-associated hyperpolarization is dependent on cholesterol-efflux and on the presence of bicarbonate in the incubation media, which induces a hyperpolarizing current. Characteristics of this hyperpolarization suggest that a Na+/HCO cotransporter activity is necessary for the regulation of capacitation in mouse sperm. An epithelial sodium channel (ENAC) localized in the midpiece also appears to play a role in regulating the capacitation-associated hyperpolarization of the sperm plasma membrane. In her talk, "Hyperactivated Motility in Sperm," Susan Suarez (Cornell University) demonstrate that the asymmetrical flagellar beat of hyperactivated sperm is adapted for traversing viscoelastic media. This type of motility enhances penetration of zona pellucida and mucus in the female reproductive tract, assists in the release of sperm from the oviductal reservoir, and may play a role in chemotaxis. Calcium is a key regulator of hyperactivated motility. Dr. Suarez identified an internal calcium store at the base of the flagellum where IP3 receptors and calreticulin are co-localized in enlarged cisternae. She proposes that release of calcium from this internal store modulates axonemal bending and initiates hyperactivated motility. Karl Swann (University College, London) presented a talk on "A Sperm-Specific PLC That Triggers Mammalian-Egg Activation." He identified a soluble phospholipase C (PLC ) in sperm and presented evidence that this novel PLC initiates calcium oscillations that activate the egg at fertilization. PLC also plays a role in the calcium oscillations that occur at the time of mitosis of the first cell cycle. Regulation of these oscillations is correlated with the release of PLC from the pronucleus when nuclear envelope breakdown occurs at the beginning of mitosis.
Symposium III, Understanding Prostate Cancer: Basic Research Advances, focused on signaling pathways involved in normal prostate growth and prostate cancer development and progression. Robert Matusik (Vanderbilt University) introduc the role of FOX transcription factors in prostate gland development and tumorigenesis in his talk, "Transgenic Models of Prostate Cancer." The endoderm-specific transcription factors, FOXA1 and FOXA2, bind to gene regulatory elements immediately adjacent to the androgen response element where they regulate androgen receptor (AR)-mediated prostate gene activation. Using transgenic mice, Dr. Matusik demonstrated a critical role for FOXA1 in epithelial cell differentiation during early development and identified this transcription factor as an upstream regulator of Nkx3.1, a prostate-specific homeobox gene. In transgenic mouse models for prostate cancer as well as in human prostate tumors, FOXA1 is overexpressed and it is hypothesized that this factor is essential for tumor growth. Daniel Gioeli (University of Virginia) spoke on "Signal Transduction and Prostate Cancer Progression." He demonstrated that Ras-MAPK activity induces androgen hypersensitivity and that the Ras-Raf-MAPK pathway is sufficient to make prostate cell lines progress to androgen independence. He provided data to suggest that AR phosphorylation at serine 650 via stress kinases is permissive for AR nuclear export and that this process, by increasing AR shuttling, may contribute to androgen hypersensitivity in prostate cancer cells. Shuk-Mei Ho (University of Massachusetts Medical School) presented a talk on "Novel Estrogenic and Anti-Estrogenic Actions in Prostate Cancer." She demonstrated that estrogen receptor b (ERb) is normally expressed in human prostate basal epithelial cells where it is purported to play anti-proliferative and anti-oxidant roles. In prostate cancer, ERb expression is lost to transcriptional silencing _as the cells advance to high grade, while ERb expression is restored at the metastatic stage. This altered expression is due to methylation and demethylation spreading from the 3’ to 5’ regions of exon 0-N, upstream from exon 1 of the ERb gene. ERb-specific ligands are being designed to regulate ERb as a therapeutic target. The advances presented in this symposium contribute to our understanding of the mechanisms involved in the initiation and progression of prostate cancer.
Many of the unexplained causes of male infertility are thought to be due to mutations in genes involved in the development and function of spermatozoa. The human and mouse genome sequencing projects have facilitated considerably the identification of such genes. Symposium IV, Genetic Causes of Male Infertility, provided examples of genes identified by both forward and reverse genetic approaches that are essential for male fertility. In his talk, "Testis Stem Cell Identity," Robert Braun (University of Washington) reported recent studies on the genetic regulation of renewal and differentiation of spermatogenic stem cells. He is studying the spontaneous luxoid mutation that leads to a progressive loss of spermatogenic stem cells in mice. Dr. Braun determined that the defect results from a nonsense mutation in the gene encoding Plzf, a transcriptional repressor. The gene is expressed in undifferentiated spermatogonia and appears to be required for stem cell self-renewal. Renee Reijo Pera (University of California - San Francisco) presented her studies on "DAZ and Related Genes Required for Germ Cell Development." The "deleted in azoospermia" (DAZ) gene was found by mapping deletions on the Y chromosome associated with male infertility. The DAZ gene family includes multiple RNA-binding proteins that are conserved and have essential roles in early germ cell development and meiosis. Dr. Reijo Pera also identified STELLAR, NANOG, and GDF3 as genes that are down regulated upon differentiation of human embryonic stem cells and map to a region of human chromosome 12 that is a hotspot for teratocarcinoma. Marco Conti (Stanford University) spoke on the "Role of Cyclic AMP in Sperm Function." He showed that both soluble adenylyl cyclase (sAC) and the olfactory type III adenylyl cyclase are expressed at high levels during spermiogenesis. He also reported that targeted disruption of the sAC gene does not have an apparent effect on spermatogenesis in mice, but dramatically impairs sperm motility and causes male infertility.
The first talk in Symposium V on Male Reproductive Tract Development addressed "Mechanisms of Testicular Descent: Cryptorchidism and Mutations of the GREAT gene." Alexander Agoulnik (Baylor College of Medicine) explained that cryptorchidism can result from failure of the cranial suspensory ligament to regress (preventing the transabdominal phase of testis descent) and/or failure of the gubernacular ligament to form properly and pull the testis into the scrotum (inguinoscrotal phase of testis descent). His research focuses on mutations in genes that control these developmental events including those encoding the insulin-like factor 3 (INSL3, a specific Leydig cell marker) and GREAT (G protein-coupled receptor affecting testis descent). Recent evidence indicates that the GREAT protein is the only cognate receptor for INSL3. The current model is that SF1 activates GREAT and INSL3. INSL3 binding to GREAT results in increased cAMP and subsequent downstream events that stimulate Leydig cell differentiation and androgen production, the latter being needed for gubernacular development and testis descent. Cory Abate-Shen (UMDNJ/Rutgers) discussed the modeling of prostate development and cancer in mutant mice in her talk "Regulation of Prostate Development." Her recent research reveals that several genes interact in the developing prostate and that disruption of these genes contributes to the development of prostate cancer. In mutant mouse models, loss of Nkx3.1 (a homeobox gene that encodes a protein important for differentiation of prostatic buds) results in abnormal ductal branching and decreased secretory proteins. With aging, these mutant mice develop prostatic intraepithelial neoplasia. Concomitant reduction of PTEN results in invasive cancer at a younger than expected age. Gene dosage of p27kip1 also plays a role in determining tumorgenicity, apparently by modifying levels of cyclin D1. Laurence Baskin (University of California - San Francisco) reviewed current evidence for the "Etiology of Hypospadias." Several mechanisms have been shown to account for a small proportion of hypospadias cases including alterations in steroid biosynthesis, defects in 5-a-reductase, damage to penile nerves, and a few rare genetic defects (as reflected in FGF-10 knockout mice). Endocrine disruptors in the environment have also been proposed as a cause, but recent epidemiologic research based on birth defects registry data and zip codes (as an indicator of living in polluted or non-polluted regions) failed to find an association between the environment and hypospadias. Although about 95% of human cases remain unexplained, recent data suggest that progesterone used for IVF may increase the incidence of hypospadias in male children and virilization in female infants. From the 176 abstracts accepted this year, twelve were selected for short platform talks. These were presented in two concurrent oral sessions, Regulation of Male Reproductive Differentiation and Function and Genetic and Environmental Factors that Disrupt Reproductive Function. The remaining abstracts were presented in two poster sessions. Specialty group events at the meeting included: the Minority Affairs Breakfast featuring Matthew Kinnard discussing the evolution of biomedical research at NIH, the Women in Andrology Luncheon with roundtable discussions of career and life issues in reproductive medicine and science, and the Lab Science Forum and Luncheon featuring Richard Saacke speaking about the principles of sperm cryopreservation. Dr. Saacke’s presentation addressed the challenges of cryopreservation, with emphasis on human needs and the effects of cryo-injury on sperm function.
Deborah O’Brien (Program Chair), Janice Bailey, E.M. Eddy, Susan Hall, John Herr, Robert Oates, Sally Perreault, Gail Prins