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Abstract
Linkage studies have defined at least five bipolar (BP) disorder susceptibility loci that meet suggested guidelines for initial identification and subsequent confirmation. These loci, found on 18p11, 18q22, 21q21, 4p16, and Xq26, are targets for BP candidate gene investigations. Molecular dissection of expressed sequences for these regions is likely to yield specific BP susceptibility alleles in most cases, in all probability, these BP susceptibility alleles will be common in the general population, and, individually, will be neither necessary nor sufficient for manifestation syndrome. Additive or multiplicative oligogenic models involving several susceptibility loci appear most reasonable at present, it is hoped thai these BP susceptibility genes will increase understanding of many mysteries surrounding these disorders, including drug response, cycling patterns, age-of-onset, and modes of transmission.
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Affiliation(s)
- W H Berrettini
- The department of Psychiatry and the Center for Neurobiology and Behavior, University of Pennsylvania, USA
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2
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Abstract
Bipolar disorder is an etiologically complex syndrome that is clearly heritable. Multiple genes, working singly or in concert, are likely to cause susceptibility to bipolar disorder. Bipolar disorder genetics has progressed rapidly in the last few decades. However, specific causal genetic mutations for bipolar disorder have not been identified. Both candidate gene studies and complete genome screens have been conducted. They have provided compelling evidence for several potential bipolar disorder susceptibility loci in several regions of the genome. The strongest evidence suggests that bipolar disorder susceptibility loci may lie in one or more genomic regions on chromosomes 18, 4, and 21. Other regions of interest, including those on chromosomes 5 and 8, are also under investigation. New approaches, such as the use of genetically isolated populations and the use of endophenotypes for bipolar disorder, hold promise for continued advancement in the search to identify specific bipolar disorder genes.
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Affiliation(s)
- Carol A Mathews
- Department of Psychiatry at the University of California, San Diego, San Diego, California, USA
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3
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Bennett P, Segurado R, Jones I, Bort S, McCandless F, Lambert D, Heron J, Comerford C, Middle F, Corvin A, Pelios G, Kirov G, Larsen B, Mulcahy T, Williams N, O'Connell R, O'Mahony E, Payne A, Owen M, Holmans P, Craddock N, Gill M. The Wellcome trust UK-Irish bipolar affective disorder sibling-pair genome screen: first stage report. Mol Psychiatry 2002; 7:189-200. [PMID: 11840312 DOI: 10.1038/sj.mp.4000957] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2001] [Revised: 05/21/2001] [Accepted: 05/21/2001] [Indexed: 11/09/2022]
Abstract
We have completed the first stage of a two-stage genome wide screen designed to identify chromosomal regions that may harbour susceptibility genes for bipolar affective disorder. The first stage screening sample included 509 subjects from 151 nuclear families recruited within the United Kingdom and Republic of Ireland. This sample contained 154 narrowly defined affected sibling pairs (DSM-IV BPI) and 258 broadly defined affected sibling pairs (DSM-IV BPI, SABP, BPII, BPNOS or MDD(R)), approximately two thirds of all families contained at least one other additional typed individual. All individuals were genotyped using 398 highly polymorphic microsatellite markers from Applied Biosystems's Linkage Mapping Set Version 2. The average inter-marker distance was 9.6 cM and the mean heterozygosity was 0.78. Analysis of these data using non-parametric linkage methods (MAPMAKER/SIBS) found no evidence for loci of major effect and no regions reached genome-wide significance for either suggestive or significant linkage. We identified 19 points across the genome where the MLS exceeded a value set for follow up in our second stage screen (MLS > or = 0.74 (equivalent to a nominal pointwise significance of 5%) under the narrowest diagnostic model). These points were on chromosomes 2, 3, 4, 6, 7, 9, 10, 12, 17, 18 & X. Some of these points overlapped with previous linkage reports both within bipolar affective disorder and other psychiatric illnesses. Under the narrowest diagnostic model, the single most significant multipoint linkage was on chromosome 18 at marker D18S452 (MLS=1.54). Overall the highest MLS was 1.70 on chromosome 2 at marker D2S125, under the broadest diagnostic model.
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Affiliation(s)
- P Bennett
- Molecular Psychiatry Group, Division of Neuroscience, University of Birmingham, Queen Elizabeth Psychiatric Hospital, Edgbaston, Birmingham, B15 2QZ, UK
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4
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Abstract
OBJECTIVES Population isolates offer several advantages for those hoping to identify predisposition genes for bipolar disorder (BP). In this review article, the rationale for performing gene mapping studies in this type of population and the results of genetic mapping studies performed to date in population isolates are presented. METHODS This article begins with a brief review of the concepts involved in mapping genes for BP. The concept of populations that show some degree of historical isolation and their special utility for certain types of gene mapping is presented. Methods of statistical analysis particularly relevant for gene mapping of complex diseases like BP are presented. Finally, several BP gene studies conducted to date in several population isolates are reviewed. RESULTS Genetic mapping studies of BP have occurred thus far in several isolates or sub-isolates, including the Amish population, Costa Ricans, Finnish, and Canadians (in Quebec), and significant linkage scores have been identified in the latter three isolates. CONCLUSIONS Possible greater homogeneity and greater consistency of diagnosis are factors that have been cited in several studies of BP done in isolates to date. Another special advantage of working in certain types of population isolate is their appropriateness for using certain types of association or linkage disequilibrium-based approaches at both the genome screening and fine mapping stages. These tests include mapping by linkage disequilibrium analyses, an approach that allows mapping to occur at the population, rather than the pedigree, level.
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Affiliation(s)
- M A Escamilla
- Neurogenetics Laboratory, Department of Psychiatry, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA.
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5
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Abstract
OBJECTIVES To review the reports of linkage findings for bipolar disorder. METHODS Literature review of published linkage findings in bipolar disorder. RESULTS There are several regions of the human genome that have been implicated repeatedly by independent investigators. These include 4p16, 12q24, 18q22, 18p11, 21q21 and 22q11. Two of these regions (18p11 and 22q11) are also implicated in genome scans of schizophrenia, suggesting that these two distinct nosological categories may share some genetic susceptibility. This hypothesis can only be tested when the underlying genes are identified.
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Affiliation(s)
- W H Berrettini
- Department of Psychiatry and the Center for Neurobiology and Behavior, University of Pennsylvania, Philadelphia, PA 19107, USA.
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Abstract
Genetic epidemiologic studies reveal that relatives of bipolar (BIP) probands are at increased risk for recurrent unipolar (RUP), BIP, and schizoaffective (SA) disorders, while relatives of schizophrenia (SZ) probands are at increased risk for SZ, SA, and RUP disorders. The overlap in familial risk may reflect shared genetic susceptibility. Recent genetic linkage studies have defined confirmed susceptibility loci for BIP disorder for multiple regions of the human genome, including 4p16, 12q24, 18p11.2, 18q22, 21q21, 22q11-13, and Xq26. Studies of SZ kindreds have yielded robust evidence for susceptibility at 18p11.2 and 22q11-13, both of which are implicated in susceptibility to BIP disorder. Similarly, confirmed SZ vulnerability loci have been mapped for 6p24, 8p and 13q32. Strong statistical evidence for a 13q32 BIP susceptibility locus has been reported. Thus, both family and molecular studies of these disorders suggest shared genetic susceptibility. These two group of disorders may not be so distinct as current nosology suggests.
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Affiliation(s)
- W H Berrettini
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19107, USA.
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7
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Abstract
OBJECTIVES To review the methodologies and findings in the genetics of bipolar disorder (BPD), and to suggest future directions for research. METHODS Reports of family, twin, adoption, linkage, association, cytogenetic, and animal model studies, and segregation analyses in English, were identified from multiple MEDLINE searches. Hand searches were carried out in bibliographies from review articles. RESULTS Family, twin, and adoption studies have provided strong evidence for a genetic etiology in BPD. Early reports of linkage of BPD to DNA markers at several chromosomal sites have not proven robust, perhaps because of the complex nature of BPD inheritance. However, linkage findings in the 1990s, on chromosomes 18, 21q, 12q, and 4p, have provided leads that are being pursued through both genetic and physical mapping. No gene has yet been definitively implicated in BPD. CONCLUSIONS Strategies for increasing the power to detect BPD genes include: (1) dividing the phenotype into genetically meaningful subtypes to decrease heterogeneity: and (2) ascertaining a very large family sample--a multicenter study now in progress will collect 700 bipolar I sibling pairs. BPD may result from several genes acting in concert so that new multilocus statistical methods could enhance the capacity to detect loci involved. Family-based association studies using a very large number of newly identified single nucleotide polymorphisms (SNPs) may allow for more efficient screening of the genome. As the Human Genome Project approaches its goal of isolating all genes by 2003, the data generated is likely to speed identification of candidate BPD genes.
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Affiliation(s)
- J B Potash
- Department of Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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8
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Abstract
Genetic epidemiological studies reveal that relatives of bipolar probands are at increased risk for recurrent unipolar, bipolar, and schizoaffective disorders, whereas relatives of probands with schizophrenia are at increased risk for schizophrenia, schizoaffective, and recurrent unipolar disorders. The overlap in familial risk may reflect shared genetic susceptibility. Recent genetic linkage studies have defined confirmed bipolar susceptibility loci for multiple regions of the human genome, including 4p16, 12q24, 18p11.2, 18q22, 21q21, 22q11-13, and Xq26. Studies of schizophrenia kindreds have yielded robust evidence for susceptibility at 18p11.2 and 22q11-13, both of which are implicated in susceptibility to bipolar disorder. Similarly, confirmed schizophrenia vulnerability loci have been mapped, too, for 6p24, 8p, and 13q32. Strong statistical evidence for a 13q32 bipolar susceptibility locus has been reported. Thus, both family and molecular studies of these disorders suggest shared genetic susceptibility. These two groups of disorders may not be as distinct as current nosology suggests.
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Affiliation(s)
- W H Berrettini
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19107, USA
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Bowen T, Kirov G, Gill M, Spurlock G, Vallada H, Murray R, McGuffin P, Collier D, Owen M, Craddock N. Linkage studies of bipolar disorder with chromosome 18 markers. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19991015)88:5<503::aid-ajmg13>3.0.co;2-u] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Knowles JA, Rao PA, Cox-Matise T, Loth JE, de Jesus GM, Levine L, Das K, Penchaszadeh GK, Alexander JR, Lerer B, Endicott J, Ott J, Gilliam TC, Baron M. No evidence for significant linkage between bipolar affective disorder and chromosome 18 pericentromeric markers in a large series of multiplex extended pedigrees. Am J Hum Genet 1998; 62:916-24. [PMID: 9529343 PMCID: PMC1377025 DOI: 10.1086/301785] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Bipolar affective disorder (BP) is a major neuropsychiatric disorder with high heritability and complex inheritance. Previously reported linkage between BP and DNA markers in the pericentromeric region of chromosome 18, with a parent-of-origin effect (linkage was present in pedigrees with paternal transmission and absent in pedigrees with exclusive maternal inheritance), has been a focus of interest in human genetics. We reexamined the evidence in one of the largest samples reported to date (1,013 genotyped individuals in 53 unilineal multiplex pedigrees), using 10 highly polymorphic markers and a range of parametric and nonparametric analyses. There was no evidence for significant linkage between BP and chromosome 18 pericentromeric markers in the sample as a whole, nor was there evidence for significant parent-of-origin effect (pedigrees with paternal transmission were not differentially linked to the implicated chromosomal region). Two-point LOD scores and single-locus sib-pair results gave some support for suggestive linkage, but this was not substantiated by multilocus analysis, and the results were further tempered by multiple test effects. We conclude that there is no compelling evidence for linkage between BP and chromosome 18 pericentromeric markers in this sample.
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Affiliation(s)
- J A Knowles
- Columbia University College of Physicians and Surgeons and New York State Phychiatric Institute, New York, NY 10032, USA
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