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Tomasi J, Zai CC, Zai G, Kennedy JL, Tiwari AK. Genetics of human startle reactivity: A systematic review to acquire targets for an anxiety endophenotype. World J Biol Psychiatry 2021; 22:399-427. [PMID: 33040669 DOI: 10.1080/15622975.2020.1834619] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVES Startle response is an objective physiological measure integral to the human defense system and a promising target for endophenotype investigations of anxiety. Given the alterations in startle reactivity observed among anxiety and related disorders, we searched for genetic variants associated with startle reactivity as they may be further involved in pathological anxiety risk. METHODS A systematic literature review was performed to identify genetic variants associated with startle reactivity in humans, specifically baseline and fear- or anxiety-potentiated startle. RESULTS The polymorphisms Val66Met (rs6265) from brain-derived neurotrophic factor (BDNF), Val158Met (rs4680) from catechol-O-methyltransferase (COMT), and the serotonin transporter-linked polymorphic region (5-HTTLPR) from the serotonin transporter gene (SLC6A4) were most commonly studied in human startle. In addition, several other genetic variants have also been identified as potential candidates that warrant further research, especially given their novelty in in the context of anxiety. CONCLUSIONS Similar to psychiatric genetic studies, the studies on startle reactivity primarily focus on candidate genes and are plagued by non-replication. Startle reactivity is a promising endophenotype that requires concerted efforts to collect uniformly assessed, large, well-powered samples and hypothesis-free genome-wide strategies. To further support startle as an endophenotype for anxiety, this review suggests advanced genetic strategies for startle research.
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Affiliation(s)
- Julia Tomasi
- Molecular Brain Science Department, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Clement C Zai
- Molecular Brain Science Department, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada.,Department of Psychiatry, University of Toronto, Toronto, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | - Gwyneth Zai
- Molecular Brain Science Department, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada.,Department of Psychiatry, University of Toronto, Toronto, Canada.,General Adult Psychiatry and Health Systems Division, CAMH, Toronto, Canada
| | - James L Kennedy
- Molecular Brain Science Department, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada.,Department of Psychiatry, University of Toronto, Toronto, Canada
| | - Arun K Tiwari
- Molecular Brain Science Department, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health (CAMH), Toronto, Canada.,Department of Psychiatry, University of Toronto, Toronto, Canada
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von Schantz M, Leocadio-Miguel MA, McCarthy MJ, Papiol S, Landgraf D. Genomic perspectives on the circadian clock hypothesis of psychiatric disorders. ADVANCES IN GENETICS 2020; 107:153-191. [PMID: 33641746 DOI: 10.1016/bs.adgen.2020.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Circadian rhythm disturbances are frequently described in psychiatric disorders such as major depressive disorder, bipolar disorder, and schizophrenia. Growing evidence suggests a biological connection between mental health and circadian rhythmicity, including the circadian influence on brain function and mood and the requirement for circadian entrainment by external factors, which is often impaired in mental illness. Mental (as well as physical) health is also adversely affected by circadian misalignment. The marked interindividual differences in this combined susceptibility, in addition to the phenotypic spectrum in traits related both to circadian rhythms and mental health, suggested the possibility of a shared genetic background and that circadian clock genes may also be candidate genes for psychiatric disorders. This hypothesis was further strengthened by observations in animal models where clock genes had been knocked out or mutated. The introduction of genome-wide association studies (GWAS) enabled hypothesis-free testing. GWAS analysis of chronotype confirmed the prominent role of circadian genes in these phenotypes and their extensive polygenicity. However, in GWAS on psychiatric traits, only one clock gene, ARNTL (BMAL1) was identified as one of the few loci differentiating bipolar disorder from schizophrenia, and macaque monkeys where the ARNTL gene has been knocked out display symptoms similar to schizophrenia. Another lesson from genomic analyses is that chronotype has an important genetic correlation with several psychiatric disorders and that this effect is unidirectional. We conclude that the effect of circadian disturbances on psychiatric disorders probably relates to modulation of rhythm parameters and extend beyond the core clock genes themselves.
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Affiliation(s)
- Malcolm von Schantz
- Faculty of Health and Medical Sciences, University of Surrey, Surrey, United Kingdom; Department of Physiology and Behavior, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
| | - Mario A Leocadio-Miguel
- Faculty of Health and Medical Sciences, University of Surrey, Surrey, United Kingdom; Department of Physiology and Behavior, Federal University of Rio Grande do Norte, Natal, RN, Brazil
| | - Michael J McCarthy
- Department of Psychiatry, University of California San Diego, San Diego, CA, United States
| | - Sergi Papiol
- Department of Psychiatry, University Hospital, Munich, Germany; Institute of Psychiatric Phenomics and Genomics (IPPG), Munich, Germany
| | - Dominic Landgraf
- Circadian Biology Group, Department of Molecular Neurobiology, Clinic of Psychiatry and Psychotherapy, University Hospital, Munich, Germany
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