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Bosun A, Albu-Kalinovic R, Neda-Stepan O, Bosun I, Farcas SS, Enatescu VR, Andreescu NI. Dopaminergic Epistases in Schizophrenia. Brain Sci 2024; 14:1089. [PMID: 39595853 PMCID: PMC11592377 DOI: 10.3390/brainsci14111089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2024] [Revised: 10/25/2024] [Accepted: 10/26/2024] [Indexed: 11/28/2024] Open
Abstract
Background: The dopaminergic theory, the oldest and most comprehensively analyzed neurotransmitter theory of schizophrenia, remains a focal point of research. Methods: This systematic review examines the association between combinations of 14 dopaminergic genes and the risk of schizophrenia. The selected genes include dopamine receptors (DRD1-5), metabolizing enzymes (COMT, MAOA, MAOB, DBH), synthesizing enzymes (TH, DDC), and dopamine transporters (DAT, VMAT1, and VMAT2). Results: Recurring functional patterns show combinations with either hyperdopaminergic effects in limbic and striatal regions or high striatal and low prefrontal dopamine levels. The protective statuses of certain alleles or genotypes are often maintained in epistatic effects; however, exceptions exist. This complexity could explain the inconsistent results in previous genetic studies. Investigating individual alleles may be insufficient due to the heterozygous advantage observed in some studies. Conclusions: Schizophrenia may not be a monolithic disease, but rather a sum of different phenotypes which respond uniquely to different treatment and prevention approaches.
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Affiliation(s)
- Adela Bosun
- Doctoral School, “Victor Babes” University of Medicine and Pharmacy, 300041 Timisoara, Romania; (A.B.); (R.A.-K.); (O.N.-S.)
- Eduard Pamfil Psychiatric Clinic, Timisoara County Emergency Clinical Hospital, 300425 Timisoara, Romania;
| | - Raluka Albu-Kalinovic
- Doctoral School, “Victor Babes” University of Medicine and Pharmacy, 300041 Timisoara, Romania; (A.B.); (R.A.-K.); (O.N.-S.)
- Eduard Pamfil Psychiatric Clinic, Timisoara County Emergency Clinical Hospital, 300425 Timisoara, Romania;
| | - Oana Neda-Stepan
- Doctoral School, “Victor Babes” University of Medicine and Pharmacy, 300041 Timisoara, Romania; (A.B.); (R.A.-K.); (O.N.-S.)
- Eduard Pamfil Psychiatric Clinic, Timisoara County Emergency Clinical Hospital, 300425 Timisoara, Romania;
- Department of Neurosciences, Discipline of Psychiatry, “Victor Babes” University of Medicine and Pharmacy, Eftimie Murgu Square 2, 300041 Timisoara, Romania
| | - Ileana Bosun
- Department of Ophthalmology, Clinical Hospital “Cai Ferate”, 300173 Timisoara, Romania;
| | - Simona Sorina Farcas
- Department of Microscopic Morphology, Discipline of Genetics, Genomic Medicine Centre, “Victor Babes” University of Medicine and Pharmacy, 2 Eftimie Murgu Square, 300041 Timisoara, Romania;
| | - Virgil-Radu Enatescu
- Eduard Pamfil Psychiatric Clinic, Timisoara County Emergency Clinical Hospital, 300425 Timisoara, Romania;
- Department of Neurosciences, Discipline of Psychiatry, “Victor Babes” University of Medicine and Pharmacy, Eftimie Murgu Square 2, 300041 Timisoara, Romania
| | - Nicoleta Ioana Andreescu
- Department of Microscopic Morphology, Discipline of Genetics, Genomic Medicine Centre, “Victor Babes” University of Medicine and Pharmacy, 2 Eftimie Murgu Square, 300041 Timisoara, Romania;
- Regional Center of Medical Genetics Timis, Clinical Emergency Hospital for Children “Louis Turcanu”, Iosif Nemoianu Street N°2, 300011 Timisoara, Romania
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Abstract
The human dopamine transporter gene SLC6A3 is involved in substance use disorders (SUDs) among many other common neuropsychiatric illnesses but allelic association results including those with its classic genetic markers 3'VNTR or Int8VNTR remain mixed and unexplainable. To better understand the genetics for reproducible association signals, we report the presence of recombination hotspots based on sequencing of the entire 5' promoter regions in two small SUDs cohorts, 30 African Americans (AAs) and 30 European Americans (EAs). Recombination rate was the highest near the transcription start site (TSS) in both cohorts. In addition, each cohort carried 57 different promoter haplotypes out of 60 and no haplotypes were shared between the two ethnicities. A quarter of the haplotypes evolved in an ethnicity-specific manner. Finally, analysis of five hundred subjects of European ancestry, from the 1000 Genome Project, confirmed the promoter recombination hotspots and also revealed several additional ones in non-coding regions only. These findings provide an explanation for the mixed results as well as guidance for selection of effective markers to be used in next generation association validation (NGAV), facilitating the delineation of pathogenic variation in this critical neuropsychiatric gene.
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