UCSF UC San Francisco Electronic Theses and Dissertations Title Candidate Gene Analysis of Panic Disorder Permalink https://escholarship.org/uc/item/5gt4f0p4 Author Hodges, Laura Michelle Publication Date 2008-06-16 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California Candidate Gene Analysis of Panic Disorder by Laura M. Hodges DISSERTATION Submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Pharmaceutical Sciences and Pharmacogenomics in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, SAN FRANCISCO Copyright 2008 by Laura M. Hodges ii Acknowledgements Principal investigator: Steve Hamilton Laboratory contributors: Oscar Bravo, Maria Bautista Oral and thesis committee chair: Laura Bull Oral committee members: Dave Glidden, Pui Kwok, Xin Chen Thesis committee members: Laura Bull, Esteban Burchard Collaborators and sample contributors: Myrna Weissman, Abby Fyer Statistical contributors: Ramiro Costa, Oleg Evgrafov, Fatemeh Haghighi Publication: Hodges LM, et al. Association and linkage analysis of candidate genes GRP, GRPR, CRHR1, and TACR1 in panic disorder. Am J Med Genet B Neuropsychiatr Genet. 2008 May 1. (Epub ahead of print)_PMID: 18452185. The material in this publication has been granted permission for reprint in this dissertation by Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc. iii Abstract Candidate Gene Analysis of Panic Disorder Laura M. Hodges Panic disorder (PD) is a common anxiety disorder of unknown etiology, with a modest contribution estimated to come from multiple genes. Although pharmacological and behavioral remedies are helpful, PD carries a significant personal and socioecomonic burden in the population. Evidence from basic and pharmaceutical research implicates a number of genes in PD. To date, among many candidate gene studies, only two candidate genes, COMT and ADORA2A, have been established to show significant association and/or linkage to PD in different study populations. Pursuing a convergence of biological, ethological, and pharmaceutical evidence, we investigated genetic variation in previously untested neuropeptide system genes (GRP, GRPR, TACR1, CRHR1), and fine- mapped the PD-linked GABA neurotransmitter receptor genes (GABRB3 and GABRA5), as risk factors for PD in 120 multiplex pedigrees. A second goal was to characterize the heritability of COMT and GABRB3 expression patterns in a control population of nuclear families, in order to identify variants in a ~440-480 kb region around the genes that may contribute to gene function. We found marginal evidence for association and/or linkage in GRP, TACR1 and CRHR1 that prohibits ruling them out as candidates for PD. Suggestive and significant evidence for linkage and association of PD to iv GABRB3 and GABRA5 encouraged mutation screens of each gene in a subset of ninety-six probands. A number of potentially functional variants, including a synonymous SNP, 5’ and 3’ untranslated region SNPs, exon-flanking SNPs, and two mutations that alter transcription factor binding sites were discovered in PD probands. In lymphoblastoid cell lines from Northern European samples represented in the HapMap, variants associated with the heritable expression of GABRB3 were located in introns and 5’ to the gene. Significant evidence for heritable COMT expression occurred for variants in genic as well as distant regions, including a gene-poor region ~340 kb from COMT, which was previously linked and associated to PD. This is the first evidence connecting potential long- range regulation of COMT expression to possible COMT dysregulation in PD. As well, nearer upstream and downstream variants to COMT were associated with COMT gene expression, providing new positional targets for putative COMT dysregulation in PD. v Table of Contents Acknowledgements...........................................................................................iii Abstract.............................................................................................................iv 1. Chapter One. Panic disorder (PD) and its genetic analysis ...................... 1 1.1. Background ............................................................................................ 1 1.1.1. Description of PD............................................................................. 1 1.1.2. Physiological traits and potential endophenotypes of PD ................ 2 1.1.3. Epidemiology of PD ......................................................................... 3 1.1.4. The etiology of PD ........................................................................... 5 1.1.5. Comorbidity and syndromic features for PD .................................... 5 1.1.6. The societal and personal relevance of PD ..................................... 7 1.1.7. Genetic studies of PD ...................................................................... 8 1.1.8. Treatment of PD............................................................................... 9 1.1.9. Fear network structures in PD ....................................................... 11 1.1.10. Candidate genes for PD............................................................... 12 1.2. Aims ..................................................................................................... 13 1.3. References ........................................................................................... 15 2. Chapter Two. Linkage and Association of Neuropeptide Genes in PD... 23 2.1. Abstract ................................................................................................ 23 2.2. Background .......................................................................................... 23 2.2.1. Pharmacological mechanisms of PD ............................................. 23 2.2.2. Effectors of the stress response system ........................................ 24 2.2.3. Pleiotropic effects of neuropeptidergic signaling............................ 27 2.2.4. Gastrin releasing-peptide signaling................................................ 29 2.2.5. Corticotropin releasing-hormone signaling..................................... 30 2.2.6. Tachykinin signaling....................................................................... 31 2.3. Methods................................................................................................ 33 2.3.1. Subject recruitment and sample collection..................................... 33 2.3.2. Genotyping methods...................................................................... 34 2.3.3. FP-TDI genotyping......................................................................... 35 2.3.4. TaqMan genotyping ....................................................................... 36 2.3.5. Linkage and association analysis................................................... 37 2.4. Results ................................................................................................. 38 2.4.1. Allelic association........................................................................... 38 2.4.2. Multimarker haplotypic association ................................................ 38 2.4.3. Two point parametric genetic linkage............................................. 39 2.4.4. Multipoint genetic linkage and non-parametric linkage scores....... 39 2.5. Discussion ............................................................................................ 40 2.6. References ........................................................................................... 43 2.7. Figures and tables................................................................................ 55 3. Chapter Three. The contribution of the chr15q12 GABRA genes to PD.. 59 3.1. Introduction........................................................................................... 59 3.2. Background .......................................................................................... 60 3.2.1. GABRA function, distribution, and gene structure........................... 60 3.2.2. Low GABRA mutability.................................................................... 62 vi 3.2.3. Evidence for anxiolysis via GABRA remodeling.............................. 64 3.2.4. Low GABAergic tone in PD recapitulated in genetic and pharmacological manipulation ................................................................. 65 3.2.5. GABAergic drugs highlight GABRA-mediated syndromes and comorbidities in PD.................................................................................. 67 3.2.6. GABRA physiology reflects PD symptoms, comorbidity, and syndromic features .................................................................................. 68 3.2.7. Subunit-specific kinetics and phenotypes of GABRB3 and GABRA5 ................................................................................................................. 73 3.2.8. Trait GABAergic differences in subjects with PD and animal models of anxiety ................................................................................................. 74 3.2.9. Gender-specific phenotypes, GABRA mechanisms, and linkage to PD............................................................................................................ 76 3.2.10. Environmental and psychological factors in GABRA dysfunction . 77 3.3. Aims ..................................................................................................... 79 3.4. Methods...............................................................................................