David Stacey, PhD*; Anbarasu Lourdusamy, PhD*; Barbara Ruggeri, PhD; Matthieu Maroteaux, PhD; Tianye Jia, PhD; Anna Cattrell, PhD; Charlotte Nymberg, PhD; Tobias Banaschewski, MD, PhD; Sohinee Bhattacharyya, PhD; Hamid Band, MD, PhD; Gareth Barker, PhD; Arun Bokde, PhD; Christian Buchel, MD; Fabiana Carvalho, PhD; Patricia Conrod, PhD; Sylvane Desrivieres, PhD; Alanna Easton, PhD; Mira Fauth-Buehler, PhD; Alberto Fernandez-Medarde, PhD; Herta Flor, PhD; Vincent Frouin, PhD; Jurgen Gallinat, MD; Hugh Garavanh, PhD; Andreas Heinz, MD, PhD; Bernd Ittermann, PhD; Mark Lathrop, PhD; Claire Lawrence, PhD; Eva Loth, PhD; Karl Mann, MD; Jean-Luc Martinot, MD, PhD; Frauke Nees, PhD; Tomas Paus, MD, PhD; Zdenka Pausova, MD; Marcella Rietschel, MD; Andrea Rotter, PhD; Eugenio Santos, PhD; Michael Smolka, MD; Wolfgang Sommer, MD, PhD; Manuel Mameli, PhD; Rainer Spanagel, PhD; Jean-Antoine Girault, MD, PhD; Christian Mueller, PhD; Gunter Schumann, MD; on behalf of the IMAGEN consortium†
Background: The mesolimbic dopamine system, composed primarily of dopaminergic neurons in the ventral tegmental area that project to striatal structures, is considered to be the key mediator of reinforcement-related mechanisms in the brain. Prompted by a genome-wide association meta-analysis implicating the Ras-specific guanine nucleotide-releasing factor 2 (RASGRF2) gene in the regulation of alcohol intake in men, we have recently shown that male Rasgrf2–/– mice exhibit reduced ethanol intake and preference accompanied by a perturbed mesolimbic dopamine system. We therefore propose that these mice represent a valid model to further elucidate the precise genes and mechanisms regulating mesolimbic dopamine functioning.
Methods: Transcriptomic data from the nucleus accumbens (NAcc) of male Rasgrf2–/– mice and wild-type controls were analyzed by weighted gene coexpression network analysis (WGCNA). We performed follow-up genetic association tests in humans using a sample of male adolescents from the IMAGEN study characterized for binge drinking (n = 905) and ventral striatal activation during an fMRI reward task (n = 608).
Results: The WGCNA analyses using accumbal transcriptomic data revealed 37 distinct “modules,” or functionally related groups of genes. Two of these modules were significantly associated with Rasgrf2 knockout status: M5 (p < 0.001) and M6 (p < 0.001). In follow-up translational analyses we found that human orthologues for the M5 module were significantly (p < 0.01) enriched with genetic association signals for binge drinking in male adolescents. Furthermore, the most significant locus, originating from the EH-domain containing 4 (EHD4) gene (p < 0.001), was also significantly associated with altered ventral striatal activity in male adolescents performing an fMRI reward task (pempirical < 0.001).
Limitations: It was not possible to determine the extent to which the M5 module was dysregulated in Rasgrf2–/– mice by perturbed mesolimbic dopamine signalling or by the loss of Rasgrf2 function in the NAcc.
Conclusion: Taken together, our findings indicate that the accumbal M5 module, initially identified as being dysregulated in male Rasgrf2–/– mice, is also relevant for human alcohol-related phenotypes potentially through the modulation of reinforcement mechanisms in the NAcc. We therefore propose that the genes comprising this module represent important candidates for further elucidation within the context of alcohol-related phenotypes.
*These authors contributed equally to this work.
†Consortium members are listed at the end of this article.
Submitted Apr. 22, 2015; Revised July 23, 2015; Revised July 26, 2015; Accepted Aug. 1, 2015; Early-released Dec. 15, 2015
Acknowledgements: This work was supported by the European Union-funded FP6 Integrated Project IMAGEN (reinforcement-related behaviour in normal brain function and psychopathology) (LSHM-CT- 2007-037286), the FP7 projects IMAGEMEND, MATRICS and the Innovative Medicine Initiative Project EU-AIMS (115300-2), as well as the Medical Research Council Programme grant “Developmental pathways into adolescent substance abuse” (93558). Further support was provided by the Swedish Funding Agency FORMAS, the German Bundesministerium für Bildung und Forschung (NGFN Plus; FKZ: 01GS08152 and eMED „Alcoholism“) and the Deutsche Forschungsgemeinschaft (DFG): Reinhart-Koselleck Award SP 383/5-1, European Research Council and FP7 SynSys (to JAG) and Ecole des Neurosciences de Paris-Ile de France (ENP) and City of Paris (to MM), Grants PS09/01979 and RD06/0020/0000 from MINECO, Spain (to ES).
Affiliations: From the Discipline of Psychiatry, University of Adelaide, Australia (Stacey); the Institute of Psychiatry, King’s College, London, UK (Lourdusamy, Ruggeri, Maroteaux, Jia, Cattrell, Nymberg, Barker, Carvalho, Conrod, Desrivières, Easton, Loth, Müller, Schumann); the MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, London, UK (Lourdusamy, Ruggeri, Jia, Nymberg, Carvalho, Desrivières, Easton, Loth, Müller, Schumann); the Institut du Fer à Moulin, UMR-S 839, INSERM and Université Pierre et Marie Curie, Paris, France ( Maroteaux, Mameli, Girault); the Department of Child and Adolescent Psychiatry, Central Institute of Mental Health, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany (Banaschewski); the University of Nebraska Medical Center, Omaha, USA (Bhattacharyya, Band); the Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland (Bokde, Garavan); the Institute for Systemic Neuroscience, UMC Hamburg Eppendorf, Hamburg, Germany (Büchel); the Department of Psychiatry, Université de Montreal, CHU Ste Justine Hospital, Montreal, Canada (Conrod); the Department of Addiction Medicine, Central Institute of Mental Health, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany (Fauth-Buehler, Mann); the CIC-IBMCC, University of Salamanca – CSIC, Spain (Fernandez-Medarde, Santos); Department of Neuropsychiatry and Cognitive Psychology, Central Institute of Mental Health, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany (Flor, Nees); the CEA, DSV, I2BM, Neurospin Bât 145 Gif-sur-Yvette, France (Frouin); the Department of Psychiatry and Psychotherapy, Campus Charité Mitte, Charité – Universitätsmedizin Berlin, Germany (Gallinat); the Departments of Psychiatry and Psychology, University of Vermont, Burlington, USA (Garavan); the Physikalisch- Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany (Ittermann); the McGill University and Genome Quebec Innovation Centre, Montreal, Canada (Lathrop); the School of Psychology, University of Nottingham, UK (Lawrence, Paus); the Institut National de la Santé et de la Recherche Médicale, INSERM Unit 1000 “Neuromaging & Psychiatry”, University Paris Sud, Orsay, and University Paris Descartes, Paris, France (Martinot); the Rotman Research Institute, University of Toronto, Toronto, Canada (Paus); the Montreal Neurological Institute, McGill University, Montreal, Canada (Paus); the Hospital for Sick Children, University of Toronto, Toronto, Canada (Pausova); the Department of Genetic Epidemiology, Central Institute of Mental Health, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany (Rietschel); the Department of Psychiatry and Psychotherapy, Friedrich- Alexander-University Erlangen-Nuremberg, Erlangen, Germany (Rotter, Müller); the Department of Psychiatry and Psychotherapy, Technische Universität Dresden, Germany (Smolka); the Neuroimaging Center, Department of Psychology, Technische Universität Dresden, Germany (Smolka); and the Deptartment of Psychopharmacology, Central Institute of Mental Health, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany (Sommer, Spanagel).
Competing interests: T. Jia has received grants from the European Union, MRC and Formas. T. Banaschewski has served in an advisory or consultancy role for Actelion, Hexal Pharma, Lilly, Medice, Oxford Outcomes, PCM Scientific, Novartis, Shire and Viforpharma; has received speaker fees from Medice, Novartis and Shire; and has been involved in clinical trials conducted by Shire and Viforpharma, all outside the submitted work. G. Barker has received teaching honoraria from General Electric Healthcare and consulting fees from IXICO. A. Bokde has received an SFI Stokes Lectureship grant from Science Foundation Ireland. K. Mann declares a grant from the European Union. M. Rietschel has received funding from the DFG, the BMBF and the European Union; as well as an honorarium from Novartis for participation on the German Alzheimer Prevention Initiative Advisory Board.
Contributors: D. Stacey, G. Barker, C. Buchel, A. Fernández-Medarde, J. Gallinat, H. Garavan, A. Heinz, B. Ittermann, K. Mann, T. Paus, Z. Pausova, E. Santos and G. Schumann designed the study. D. Stacey, B. Ruggeri, M. Maroteaux, A. Cattrell, C. Nymberg, T. Banaschewski, S. Bhattacharyya, H. Band, A. Bokoe, F. Carvalho, S. Desrivières, A. Easton, M. Fauth-Bühler, H. Flor, J. Gallinat, H. Garavan, A. Heinz, B. Ittermann, G. Lathrop, C. Lawrence, E. Loth, J.-L. Martinot, F. Nees, T. Paus, M. Rietschel, A. Rotter-Neubert, M. Smolka, C. Mueller and G. Schumann acquired the data, which D. Stacey, A. Lourdusamy, T. Jia, C. Nymberg, P. Conrod, V. Frouin, M. Rietschel, W. Sommer, M. Mameli, R. Spanagel, J.-A. Girault and G. Schumann analyzed. D. Stacey, A. Lourdusamy, T. Jia, P. Conrod, K. Mann, T. Paus and G. Schumann wrote the article, which all authors reviewed and approved for publication.
Members of the IMAGEN consortium: Gunter Schumann, Anna Cattrell, Herta Flor, Frauke Nees, Tobias Banaschewski, Arun Bokde, Rob Whelan, Christian Buechel, Uli Bromberg, Patricia Conrod, Vincent Frouin, Dimitri Papadoulos, Juergen Gallinat, Hugh Garavan, Andreas Heinz, Henrik Walter, Bernd Ittermann, Penny Gowland, Tomáš Paus, Luise Poustka, Jean-Luc Martinot, Herve Lemaitre, Eric Artiges, or Marie-Laure Paillère Martinot, Michael N. Smolka, Eva Mennigen, Nora C. Vetter and Sarah Rodehacke.
Correspondence to: D. Stacey, Discipline of Psychiatry, Level 4, Eleanor Harrald Building, Frome Road, University of Adelaide, Adelaide, 5005, Australia; email@example.com