Genetics of Depression: Psychotic forms of Unipolar and Bipolar Disorder

1. Genetics of Depression: Psychotic forms of Unipolar and Bipolar Disorder J. Raymond DePaulo, Jr., M.D. Henry Phipps Professor and Director Department of Psychiatry and Behavioral Sciences Johns Hopkins University School of Medicine

2. 17 Years after the 1st Genomic Map, Why don’t we have the Depression Genes? • Family Samples, Genome Maps and Linkage Analyses were developed in order to find the genes. What happened? • Association Studies are being published at a rapid rate. What to make of them? • What should we do now? • More Genome Scans? Linkage, Association, Expression, Methylation, Duplication-Deletion, and other scans are possible. • Candidate Gene Studies? Association, Expression, Gene-Environment Interaction Studies, Genetic Neurobiology, and Protein-Protein Interaction Studies. • Reduce the Genetic Investment? In the U.S., NIH is short on money while patient-advocacy & legislators want new treatments.

3. 17 Years after the 1st Genomic Map, why don’t we have the Depression Genes? • 1. What Happened in the Linkage Analyses? Depression and BP are complex. Linkage works best for single gene disorders. Linkage is working here too but slowly & imprecisely. • 2. What to make of the Association Studies that are being published now? Be skeptical but hopeful. The biotech experts remind us to remember that “90% of positive results will be false positives,” when you are exploring. • 3. What to do now? Do more genetic studies & others also. The optimal design for genetic studies won’t be known until we find the genes!

4. Editorial The Genetics of Bipolar Disorder: Where Do We Stand? The The Dairuma Dashi: “Fall down seven times, stand up eight times.” Thomas Edison: “Hell, there are no rules here. We are trying to accomplish something.” American Journal of Psychiatry 161 (April): 595-597, 2004

5. Goals of Psychiatric Genetics • Isolate key genes in the brain pathway of disorders (e.g. Alzheimer’s) • Genes will: • Guide the development of diagnostic tests • Predict treatment responses • Illuminate environmental risk& protectivefactors • Illuminate pathogenesis • Initiate translational research, i.e., developing new treatments based on basic biology of a disease

6. 8 Consensus Linkage Regions In Bipolar Disorder 4p16 18p11** 22q11-13** 12q24 13q32** 18q21-23 21q22 4q35

7. Chromosomal locations of credible schizophrenia candidate genes: 35 32 31 22 21 13 21 23 24 25 31 32 42 Ch. 1 Ch. 22 p PRODH COMT APOL q RGS4 Adapted from Cloninger CR, PNAS 99(21):13366 DISC-1

8. Am. J. Hum. Genet. 74:1154–1167, 2004 Genomewide Significant Linkage to Recurrent, Early-Onset Major Depressive Disorder on Chromosome 15q Peter Holmans, George Zubenko, Raymond Crowe, J. Raymond DePaulo , William Scheftner, Myrna Weissman, Wendy Zubenko, Sandra Boutelle,Kathleen Murphy-Eberenz, Dean MacKinnon, Melvin McInnis, Diana Marta, Philip Adams, James A. Knowles, Madeleine Gladis, Jo Thomas, Jennifer Chellis, Erin Miller, and Douglas Levinson University of Wales College of Medicine, MRC Biostatistics Unit, United Kingdom; University of Pittsburgh, Pittsburgh; University of Iowa, Johns Hopkins University, Rush University Medical Center, Columbia University, and New York State Psychiatric Institute and University of Pennsylvania Genomewide significant linkage observed on 15q25-26,ZLR= 4.14 (equivalent LOD =3.73) in 297 families with 415 independent affected sib pairs. Needs Replication.

9. Am. J. Hum. Genet. 76:237–248, 2005 Genomewide Scan for Affective Disorder Susceptibility Loci in Families of a Northern Swedish Isolated Population Tine Venken, Stephan Claes, S Sluijs, Andrew Paterson, Cornelia van Duijn, Rolf Adolfsson, Jurgen Del-Favero, Christine Van Broeckhoven Suggests linkage at 9q31-q34 (MPLOD 3.22) and 6q23-q24 (MPLOD 3.25)

10. After Linkage tasks are…. • Identify Candidate Genes • Find Mutation(s) in the gene (expect > 1 mutation per gene as in Breast Cancer story) • Assess Frequency of mutation(s) in cases compared to controls • Prove Pathogenicity: How do pathogenic alleles of gene cause pathology (and how do protective ones protect)? • This next step could be impossible: • Pathophysiology: How does the pathology lead to development of the psychological features of syndrome? • How and where in the pathways would you intervene to prevent or cure the disorder?

11. Region Of Conserved Sequence Around G72/G30 in BP Sample* G72/G30 Gene Locus, on 13q33, Associated with Bipolar Disorder *Hattori et al, Am J Human Genetics, 2003

12. P2X7R is a BP candidate gene on 12q24…based on linkage, association, and functional studies (knockout and agonist studies) in mice. Barden et al, 2004 P2X receptors are ATP-gated cation channels that mediate fast excitatory transmission in diverse regions of the brain and spinal cord. Several P2X receptor subtypes have the unusual property of changing their ion selectivity during prolonged exposure to ATP. Brief exposure to ATP induces the opening of channels that are permeable to both mono- and divalent cations, whereas more sustained exposures result in progressive dilatation of the channel pore. The P2X7R was originally described in cells of hematopoietic origin, in which its activation has been linked to cell lysis, an apparent consequence of efflux of essential metabolites and intracellular messengers. Although the P2X7R has been found in the nervous system, its functional role in the brain has remained relatively unexplored. Wang et al, Nat Med 10:821, 2004

13. TPH2 SNP Polymorphisms in Unipolar Disorder Zill et al, 2004

14. FKBP5 genotype and Depression Binder et al, 2004 Nature Genetics FKBP5 Gluco-Corticoid Receptor Chaperone

15. JHU Clinical Study: Psychosis is familial Potash et al., 2001

16. Do Psychotic Symptoms Cluster in some BP Families? Data from 65 + 69 BP I proband family sets: Potash et al, Am J Psychiatry, 2001; Potash et al, Neuropsychiatric Genetics, 2002

17. Psychotic BP Linkage Potash et al. 2003

18. Genetics BP & UP, circa 2005: • Linkage studies of psychiatric disorders are very blunt instruments but they have guided us to… • Several credible candidate genes for Schizophrenia, based on location and function, which are now supported and replicated. Candidate mutations exist for 2,COMT & DISC1 • At least one candidate (G72) has been supported and replicated in BP Disorder. Other candidates for BP and UP include P2X7R on 12q (Barden et al, 2004) & XBF. • Several Schizophrenia and BP/UP related linkages, associations and candidate genes have emerged. Their salience and relationships remain to be explained.

19. Future Research Directions • Genome-wide association studies are now feasible (high quality genotypes at $ 0.01 per genotype) and more powerful for complex genetic disorders. • Phamacogenetics is now possible on a large scale. • Gene-Environment and Gene-Gene studies. • Hypothesis driven studies to determine which phenotype subtypes are associated with which gene or set of genes. • Studies of the neurobiology of candidate genes and endophenotypes are proving particularly useful. • These will lead not only to better diagnosis and treatment predictions but to true understanding of BP and rational approaches to treatment. It will also inform our education of patients, families, and policy makers….stay tuned

23. DRPLA HD Experimental Pathology:Intranuclear Inclusions in HD Mouse and Human HD Mouse Model: HD mouse model labeled Huntingtin antibodies HD Patient Brains labeled Huntingtin Antibodies and DRPLA w atrophin-1

24. Merikangas and Risch, Am J Psychiatry, 2003

25. BP& UP Disorder: Disease Paradigm Phenotype Clinical Syndrome Pathophysiology Brain Pathology Pathological Disease Entities Pathogenesis Etiology Genes McHugh & Slavney, 1998; Lewis DA, 1999

26. Clinical Hypotheses and Bipolar Genes Anticipation: McInnis et al,1993 Triplet Repeat Search: Margolis,Swift-Scanlon 2001, 2004 Parent of origin: McMahon,’95,’97; Stine,’95 Mitochondrial study: McMahon and Wallace , 2001 Imprinted Gene Search: Potash and Feinberg Co-morbid panic disorder: MacKinnon,’96, ’98 Rapid Cycling, Rapid Switching: MacKinnon, 2003, 2004 Episode Frequency: Fisfalen et al, 2004 BP II: Simpson et al, 1993; McMahon, 2001, Nwulia, 2004 Psychotic Bipolar Disorder: Potash, 2001, 2002, 2003

27. BP Meta Analyses: Badner and Gershon, 2003;Segurado et al, 2003

28. Relative Risks for Selected psychiatric disorders • Disorders Relative RiskHeritability • Bipolar 7-10 60-70% • Unipolar 2-3 28-40%* • Schizophrenia 8-10 80- 84% • Panic Disorder 3-8 50-60% • Autism 50-100 90% Merikangas and Risch, Am J Psychiatry, 2003

29. Paternal haplotype sharing in 18q22 by diagnosis of affected sibling pairs (families # 1-28) McMahon et al, 2001

30. Paternal haplotype sharing in 18q22 by diagnosis of affected sibling pairs (in families # 29-58) McMahon et al, 2001

31. Schizophrenia-susceptibility genes and synaptic plasticity Harrison PJ & Owen MJ, 2003

32. Genes for schizophrenia NRG1 = neuregulin-1 DTNBP1 = dysbindin DAAO = D-aminoacid oxidase RGS4 = regulator of G-protein signalling-4 PRODH=proline dehydrogenase COMT=catechol-O-methyltransferase *Some case-control studies negative. Harrison PJ & Owen MJ, 2003

33. James Potash Dean MacKinnon Peter Zandi Francis Mondimore Virginia Willour Haiming Chen Evaristus Nwulia Jennifer Payne Kay Jamison Susan Folstein Francis McMahon- NIMH Melvin McInnis- Michigan Sylvia Simpson -Colorado Barbara Schweizer Erin Miller Gwen Walker Brandi Craighead Jenn Coughlin Lawrence Lan- Nat Univ Taiwan Ann Heinzer Yuqing Huo Anne Phillips- Vanderbilt Jenn Coleman Jen Chellis- University of Utah Theresa Swift-Scanlan Jo Thomas Steel- NIMH Johns Hopkins Bipolar Genetics Team

34. Associationof G72/G30Locus, on 13q33, with Bipolar DisorderHattori et al, Am J Human Genetics, 2003 Replications now by Chen et al, 2004 and Schumaker et al, 2004

35. The Alzheimer's Amyloid Pathway   BACE1 Secretase cleavage APP Cell C- -N Lumen b (BACE1) cuts first  cuts first A Insoluble Hard to clear Toxic Soluble Easier to clear

36. Genetic linkage results for 32 markers on chromosome 18q21-23 McMahon et al, Arch Gen Psychiatry, 2001

37. TPH2 SNP Polymorphisms in Unipolar Disorder Zill et al, 2004

38. Polymorphisms in FKBP5 are associated with increased recurrence of depressive episodes and rapid response to antidepressant treatment Binder E, Salyakina D, Lichtner P, et al, NATURE GENETICS, 2004

39. Why so much money and for what? • The Genome Project makes psychiatric genetics possible or so we think according to skeptics. • The successes with monogenic disorders (CF) or at least diseases with some monogenic forms (Alzheimer’s) has been good to excellent • Are we making real progress in BP? • Gene Identification in Schizophrenia, relevance to Bipolar Disorder • Clinical Analysis > Clues to Genetic Heterogeneity • Conclusions, Future Directions, Collaborators

40. Translational Research “A translational researcher is someone who takes something from basic research to a patient and measures an endpoint in a patient.” Source: Lee Nadler, senior V.P. for Experimental Medicine, Dana Farber Cancer Institute, quoted in Nature Medicine, July 2002.