Gender-Specific Medicine and the Genome: A Complex and Evolving Tale

1. Gender-Specific Medicine and the Genome:A Complex and Evolving Tale Marianne J. Legato, M.D., F.A.C.P. Professor of Clinical Medicine, Columbia University Director, Partnership for Gender-Specific Medicine at Columbia Adjunct Professor of Medicine, Johns Hopkins

2. The past twenty years have witnessed a profound series of changes in our approach to and our achievements in biomedical investigation. As a result, we have a radically new view of normal human biology and the pathophysiology of disease and indeed, of the nature of life itself. Instead of “what are the differences between male and female?”, many scientists are asking: “What does it mean to be human?”

3. Traditional Biomedical Research Has • Made men normative for the entire population. Paradoxically, there has not been a systematic consideration of their unique, gender-specific features. • Not grappled with the extraordinarily difficult and most important issue of teasing out what characteristics are hard-wired as a result of biological sex and which are the consequence of social forces and environment.

4. Critics of the biomedical model have demonstrated that: “What is normal depends on who is being compared to whom, that many diseases have social and environmental causes that illness rates and severity vary from place to place, and that the values underlying medical research, practice, theories and knowledge are deeply biased by the practice situations and social characteristics of the dominant group of medical professionals-physicians.” J. Lorber. Gender and the Social Construction of Illness. Sage Publications, Thousand Oaks, CA 1997. Quoted by Bird CE in 10.1016/50277-9536(98)00420-X

5. What Influences “Health”? • Biomedical and sociologic experts often disregard and even disparage each other, particularly when funding is scarce. • Assumptions about health influence practice (The notion that women are relatively immune to coronary artery disease is still deep seatd in medical practice.) • There are gender differences in • health behaviors of men and women • the level of attention given to preserving male and female health • the societal roles expected of males and females. These patterns may shift over time. • Anne Fausto- Sterling: without absolute social equality we cannot know the absolute differences between men and women.

6. What Influences Biomedical Investigation? • Public interest • The investigator: Innate ability. Previous experiences and training. Prejudices and misconceptions.

7. 1990-2010: How Far Have We Comeand Where are We Now? • We are more aware of the extent and complexity of the sex and gender specific properties of living organisms. • We are exploring how the intricate dance between the genome, hormones and the environment creates the phenotype. • We are inserting mechanical components into humans, including into their brains. We are also creating completely mechanical entities; robots capable of heretofore unimagined complex maneuvers. • The new age of synthetic biology is transforming our understanding of what constitutes life. For the first time in the history of the world we have the power to generate new forms of life, themselves capable of reproduction.

8. Modern Scientific Investigation: 1940’s to 1980’s The Bikini View of Women’s Health

9. The New Science of Gender-Specific Medicine And the Beginning of the Genomic Era 1988- Direct Investigation of Women 2000: Genomic Medicine 2000: Robots 1994-2000 Gender- Specific Medicine 2003: ENCODE 2010: Synthetic Biology

10. Some Important Issues • Is it everpossible to separate what is hard-wired into the organism by virtue of biological sex and what is the result of the impact of other factors on the phenotype? • What is the impact of biological sex on gene expression? • Given the complexity of how the phenotype is determined, how powerful/useful will the delineation of an individual’s genome be in predicting disease and in choosing therapy? • To what extent will mechanical parts augment human abilities? What does it mean to be ‘human’? • What role will synthetic biology play in the nature of life on this planet?

11. Is it ever possible to separate what is hard-wired into the organism by virtue of biological sex and what is the result of the impact of other factors on the phenotype?

12. “Sex-specific?” “Gender-specific?” (It is impossible to separate the organism from its experience.)

13. “There is no gene-controlled inheritable trait that cannot be altered by the environment…Humans enter the world as a work-in-progress…Nature/nurture is not an either/or duality but, rather, represents a both/and type of complementarity.” The Complex Dance Between the Genome And Experience: Environmental Epigenomics. Leonard Schlain. Sex. Time and Power. Penguin Books. New York. 2003.

14. How Environmental Factors Impact the Phenotype • Environmental factors act by • mutating promoter and coding regions of genes • modifying CpG methylation at critically labile genomic regions. (Waterland R and Jirtle R. Nutrition 20:63.2004) • Epigenetic mechanisms include chromatin folding and attachment to the nuclear matrix, packaging of DNA around nucelosomes, covalent modifications of histone tails and DNA methylation. (Dolinoy DC and Jirtle RL.Environ. Mol Mutatgen.49:4.2008) • Regulatory small RNA’s and micro RNA’s impact gene transcription.(Matzke M and Birchler J. Nat Rev Genet 6:24.2005)

15. How Experience Changes the Brain • Neural changes associated with environmental enrichment: increase in brain size, cortical thickness, neuron size, dendritic branching, spine density, synapses per neuron and glial numbers. (Kolb B and Whishaw IQ. Annu Rev Psychol.49:43.1998) • Modulation of Experience-dependent Change • Age: neuronal loss and dendritic growth: an area of controversy. • Sex hormones: essential to sex-specific development of the brain and to maintain the sex-specific characteristics of the brain throughout life. (Stewart J and Kolb B. Behav.Neural Biol.49:344.1988 and Brain Res.654:149. 1994.) • Neurotropins • Stress: • chronic excess of glucocorticoids is toxic to neurons. (Sapolsky RM. Stress, the Aging Brain and Mechanisms of Neuronal Death. MIT Press. 1992) • Early life experience and major stressful life events produce dysregulation of serotonergic systems. (Gardner LK et al. Brain Research Elsevier.2009)

16. The New World of Genomic Science June 26,2000: The White House announces the completion of a rough draft of the human genome. April 14, 2003: The Human Genome Project announces a much more complete and accurate version.

17. Gender and the Genome: Why do we have two sexes? How do they differ? Which is hardier?

18. Sexual Dimorphism is Achieved Not Only by Gonadal Hormones but by the Direct Effect of X and Y Genes. The discovery of the gynandromorphic zebra finch: this bird has male plumage and a testis on the right side of the body and female plumage and an ovary on the left side. the brain was also sexually dimorphic; brain tissue on the right was genetically male and that on the left female. The hormonal milieu of the bird was obviously homogeneous.* *Agate RJ et al. Proc. Natl. Acad Sci USA100:4873 2003

19. The X chromosome* • Contains 1,098 genes; only 4% of all human genes: gene density is low and gene length is lower than any other of the chromosomes annotated to date. (Furthermore, only 33% of the chromosome is transcribed.) • Only 54 of these genes have functional homologues on the Y chromosome. • Many of the genes that have to do with intelligence may be located on the X chromosome and may be closely linked with a gene dictating preference for intelligent males. • Almost 10% of diseases with a mendelian pattern of inheritance are X-linked. *Ross MT et al. The DNA sequence of the human X chromosome. Nature 434:325-337. 2005.

20. The Y Chromosome:a New View “Functional or developmental themes have rarely been ascribed to whole chromosomes in eukaryotes. instead, individual chromosomes appear to contain motley assortments of genes with extremely heterogeneous patterns of developmentally regulated expression. We speculated that the human Y chromosome might be a functionally coherent exception…”* *Lahn BT and Page DC. Functional Coherence of the Human Y chromosome Science.278:675-680.1997

21. The Y Chromosome:Revising the Wasteland Model* • It is an unique chromosome: • Common ancestry and persistent relationship with the X chromosome • Present only in males • Does not combine with its partner along 95% of its length (called the NRY or non-recombining portion of the Y chromosome) • Tendency of its genes to degenerate during evolution • Unique coherence of gene content • Contains 78 genes (almost double the previously known tally) which make up <1% of the genome.They encode only 28 distinct proteins. • The Y chromosome can repair itself as a result of its palindromic structure. A backup copy of each of the genes they contain exists at each end of the sequence. Lahn BT and Page DC. Functional Coherence of the Human Y Chromosome. Science 278:675-680.1997

22. Male Driven Evolution* • Almost all new mutations are derived from the father. (Makova KD and Li WH. Nature 416:624-26.2002) • Oocytes spend most of their lives in relative dormancy . Sperm are produced in huge numbers and have much higher metabolic requirements. • Male: female mutations in primates is about 3-6:1. Mutations result from • Replication errors • DNA fragmentation • Variability in the male germ line creates the genetic diversity that fuels the evolutionary process. *Aitken RJ and Krausz C. Oxidative stress, DNA damage and the Y chromosome. Reproduction 122:497-506.2001

23. Given the complexity of how the phenotype is determined, how powerful/useful will the delineation of an individual’s genome be in predicting disease and in choosing therapy?

24. “Skepticism about genomics runs high…. Some …perceive genomics research as a low-yield investment at best and as a dangerous opportunity cost at worst, which undercuts efforts to address social and environmental causes of ill health.”

25. Combining Genomics with Epidemiology:Balancing Population Based with Individually Targeted Prevention/Treatment Strategies. • Is increasing attention to genomics useful for the public health? • Will it widen the gap between richer and poorer members of society? • Will it reinforce racial stereotyping? • Will it lead researchers to miss factors that contribute to disparities more substantially than genomics? • The new science of human genome epidemiology: assesses* • Prevalence of gene variants in different populations • Magnitude of disease risk associated with gene variants • Magnitude of disease risk associated with gene-gene and gene-environment interactions • Validity and effectiveness of genetic tests for screening and prevention. Khoury MJ et al. Am J Prev Med 33(4).310-317.2007

26. “The question of how genes are defined and regulated is deceptively simple. The emerging picture of gene regulation depicts interdependent layers and webs of control consisting of interactions of DNA with regulatory proteins and RNA molecules that are akin to the interactions that occur in computer circuitry.”* Feero WG et al. N Engl. J. Med 362:21.May 27, 2010

27. The Human Genome Project:Is It the Holy Grail?*:The Notion of Biological Determinism • “The assumption that genes are the carrier of our destiny... places reductionist explanations to behavior above all others and, in so doing, allocates other causes such as environment to subsidiary roles.” • Genes are not the determinant mechanism in a biological process, but part of an interaction between the genes and the organism as a whole. • Organicism: a more complex and less popular view, which maintains that reductionism is inadequate to explain living systems. It maintains that one must look at the organizational structure of the organism, not just its disparate parts. Morse A. Searching for the Holy Grail: the Human Genome Project and Its Implications.J Law & Health.13:1-34.1998.

28. “The idea that the human genome can be the Rosetta Stone for disease ignores physical, chemical and environmental factors.* Keller EF. Master Molecules, in ARE GENES US? Carl F. Cranor ed. 1994.

29. What is the impact of biological sex on gene expression?

30. The Genetic Gender Gap: The Sexually Dimorphic Gene* • Thousands of genes showed sexual dimorphism in liver, adipose and muscle; hundreds of genes were sexually dimorphic in brain. • These differences are highly tissue specific; thousands of genes identified were involved in tissue-specific biological functions and/or pathways relevant to common diseases and showed tissue-specific chromosomal enrichment. • Only 27 genes showed consistent direction , i.e. all female or all male biased in all tissues. • A significant portion of sexually dimorphic genes are located on the sex chromosomes, but some are carried on autosomes as well. *Yang X et al. Tissue-specific expression and regulation of sexually dimorphic Genes in mice. Genome Research.16:995-1004.2006

31. Sex Impacts Gene Expression* “We saw striking and measurable differences in more than half of the genes’ expression pattern between males and females. We didn’t expect that. no one has previously demonstrated this genetic gender gap at such high levels.”** **Thomas Drake, C0 investigator *Yang et al. Genome. 2006

32. TheGenomic Era Is manipulating the genome interfering with evolution or by definition, a continuation of the process?

33. What Scientists are Doing • Taking genes out and inserting others. • Creating biologic specimens capable of reproduction. • Giving us an increasingly precise picture of who we are and the possibility of changing it.

34. Evolution is no longer “natural selection”. With the advent of genetic engineering, we can- and are- changing very nature of created life.

35. Imagine: Human cloning Engineering the characteristics of new (human?) beings prepared for specific functions (like war, for example) Prolonging the life span indefinitely Creating new biological systems capable of reproduction (and if this is so, also capable themselves of evolution)

36. Genomic Science and Sex • Will it be an advantage to retain two sexes? • If we eliminate biological sex in new forms of life before we understand the nature and extent of its expression on genes, what will be the consequences to form and function? • Does the study of the impact of sex on gene expression deserve more attention? Genomic scientists are not always considering the impact of biological sex on their data.

37. “If the molecular, cellular, and genetic machinery used to conceive, develop, and operate a human were designed rather than the result of evolution, humans would be different and life would look different.”* *Olshansky et al. What if Humans were Designed to Last? The Scientist. 21(3).28

38. What are scientists worrying about?

39. Consider the Impact OfGenomic Science On • The environment • Economics • The nature and number of living beings • The redistribution of power (planned and unplanned)

40. “I chide Goldblatt* for the incredible naiveté he and the Defense Sciences Office displayed in not thinking its plans to enhance humans would arouse controversy…. didn’t it occur to anybody that you were playing with fire?” Joel Garreau (in Radical Evolution) *Michael Goldblatt, former head of the Defense Science Office

41. What Scientists are Saying • We are changing the rate and mechanisms of the evolution of living things profoundly. • If there is a choice between preserving the earth in a viable state or continuing the human race, we will probably opt to continue the race.

42. “My guess is that if the question of human extinction is ever posed clearly, people will say that it’s all very well to say we’ve been a part of nature up to now, but that at this turning point in the human race’s history, it is surely essential that we do something about it; that we fix the genome to get of rid of the disease that’s causing the instability, if necessary, we clone people known to be free from the risk, because that’s the only way in which we can keep the human race alive. A still, small voice may at that stage ask, but right does the human race have to claim precedence for itself. To which my guess is the full-throated answer would be, sorry, the human race has taken a decision, and that decision is to survive. And, if you like, the hell with the rest of the ecosystem.” Sir John Maddox, Former editor of Nature

43. Synthetic biology: The ability to create living organisms from inert chemicals. These new entities will probably be capable themselves of reproduction and of evolution into new forms.

44. Venter’s group has just reported the design, synthesis and assembly of a genome and its transplantation into a recipient cell to create new cells that are controlled only by the synthetic chromosome.* Gibson DG et al. Sciencexpress./www.sciencexpress.org/20 May 2010/Page 1.

45. Venter’s Achievement:Reactions • Obama urges Presidential Commission for the Study of Bioethical Issues to focus on the research: “This development raises the prospect of important benefits….at the same time it raises genuine concerns…”. • George Church: “This milestone and many like it should be celebrated…But…the semi-synthetic myobacterium is not changed from the wild state in any fundamental sense. Printing out a copy of an ancient text isn’t the same as understanding the language.” • Arthur Caplan: “Venter and his colleagues have shown that the material world can be manipulated to produce what we recognize as life…Christianity, Islam and Judaism, among other religions, have maintained that a soul constitutes the explanatory essence of at least human life….All of these…views are cast into doubt by the demonstration that life can be created from non-living parts…” • Martin Fussenegger: “Venter…calls this ‘going from reading our genetic code to the ability to write it.” It may sound scary, but there is no guarantee that what will be written will make sense.”

46. Doctor Atomic "Ever since the discovery of nuclear fission, the possibility of powerful explosives based on it had been very much in my mind, as it had in that of many other physicists. We had some understanding of what this might do for us in the war, and how much it might change the course of history.” “I am become death, destroyer of worlds.”

47. Doctor Genomic George Church Professor of Genetics at Harvard Medical School Director of the Center for Computational Genetics. “…synthetic biology shares the potential…to generate new entities that reproduce and evolve at will. Whether we believe that these are immediate, distant or imaginary threats, the concerns are real….in addition to a code of professional ethics for synthetic biologists, we need to watch for the rare cases where they transgress.”

48. “Given the momentum and international character of research in synthetic biology, it is already too late to impose a moratorium, if indeed one was ever contemplated.”* Tucker and Zilinskas: The Problems and Perils of Synthetic Biology. In The New Atlantis. A Journal of Technology and Society.

49. Prometheus, who gave men fire.

50. What Are Areas of Special Interest As We Go Forward? • Focusing a gender-specific lens on men, so that we can better understand their greater vulnerability compared with women. • Expanding the current science of gender-specific medicine and testing its value in clinical practice. • Urging the exploration of the impact of biological sex on both the naturally occurring and synthetically created/altered genome. • Encouraging the colloquium between jurists, ethicists and scientists about the legal and moral implications of genomic science and synthetic biology.